Download Study Guide for Electrons Mini-Test - seys

Science 8
My study guide for Electrons Mini-Test
Marina Chan
12/11/08 – 12/15/08
Chemical Interactions - 1.2 - Elements make up the periodic table
Elements can be organized by similarities:
one way of organizing elements:
- masses of their atoms
- not all the atoms of an element have the same atomic mass number = isotopes
- when finding mass of an atom = finding the average mass of all its isotopes
- atomic mass: the average mass of all the element’s isotopes
Mendeleev and predicting new elements:
1860s: Dmitri Mendeleev, a Russian chemist began thinking about how he could
organize the elements based on their physical and chemical properties
- made a set of element cards
- atomic mass of an atom of an element
- any information about elements’ properties
- he tried to arrange the cards in various ways looking for a relationship between
properties and atomic mass = led to listing elements in a chart
- rows of the chart: placed elements showing similar chemical properties
- arranged rows so the atomic masses increased as one moved down each vertical
column
1869: Mendeleev produces the first periodic table of the elements
- shows a periodic, or repeating, pattern of properties of the elements
- left some empty spaces where no known elements fit the pattern: predicted that new
elements that would complete the chart would eventually be discovered
- he described some properties of these unknown elements
- after six years he published table: first of these elements was discovered =
gallium
- in the next 20 years, two other elements predicted would be discovered
Reading the periodic table:
modern periodic table
- elements with similar properties are found in columns
- elements are arranged by atomic number
reading the periodic table:
- each square of the periodic table give particular information about the atoms of an element:
- number at top = atomic number: the number of protons in the nucleus of an atom of
that element
- chemical symbol: an abbreviation for the element’s name
- contains one or two letters
- (some elements that have not yet been name = designated by temporary threeletter symbols)
- name of element
- average atomic mass of all the isotopes of the element
- color of the elements’ symbol = indicated the physical stated of the element at room
temperature
- white letters = indicate a gas
- blue letters = indicate a liquid
- black letters = indicate a solid
- background colors of the squares = indicated whether the element is a metal, nonmetal or
metalloid
Groups and periods:
group: a vertical column in the periodic table = elements in a group share similar properties
- labeled by a number at the top of the column
- sometimes a group is called a family of elements = because elements seem to be
related
- members of a family of elements are related but not identical
- trends
- from top to bottom
- atomic size increases
- density usually increases
- Group 17 = halogen group
- tend to combine easily with many other elements and compounds, especially elements
in Groups 1 and 2
- although have some similarities = physical properties are not always the same
- lithium, sodium, potassium = all in Group 1
- react violently if they come in contact with water
period: a horizontal row in the periodic table = properties of elements change in a predictable
way from one end of a period to the other / the chemical properties of the elements show a
progression
- elements in a period have varying properties
- trends
- from left to right
- atomic mass increases = one proton and electron are added to each element
- atomic mass number increases (usually)
- atomic size decreases
- ions
- elements on left = form positive/negative ions easily (primarily a
positive ion because it’s easier to loose an electron than gain one)
- elements on right = don’t form ions (not easily)
- density:
- elements on left and right = least dense
- elements in middle = most dense
- Period 3 = contains elements with a wide range of properties
- elements on far left = metals
- elements on far right = nonmetals
Trends in the periodic table:
the periodic table organizes elements by properties = an elements position in the table can give
information about the element
- formation of ions
- left side of the table = atoms of elements form positive ions easily
- Group 1 = can lose an electron for form ions with one pos. charge (1+)
- Group 2 = can lose two electrons to form ions with a charge of 2+
- right side of the table = harder for atoms of elements to form positive ions
- Group 18 = normally do not form ions at all
- Group 17 = often gain one electron to form a negative ion (1-)
- Group 16 = can gain two electrons to form a 2- ion
- Group 3-12 = all form positive ions, but the charge can vary
- size of an element’s atoms
- groups (to bottom) = atomic size increases
- periods (to right)= atomic size decreases
- density
- groups (to bottom) = density generally increases
- periods = elements on left and right = least dense / elements in middle = most
dense
Chemical Interactions 1.3 - The periodic table is a map of the elements
The periodic table has distinct regions:
- an atom’s position on the periodic table indicates the properties of its element
- the periodic table has three main regions:
- metals on the left (yellow on the periodic table)
- metalloids in the middle (purple on the periodic table)
- nonmetals on the right (except hydrogen) (green on the periodic table)
- position indicates how reactive an element is
- reactive: indicates how likely an element is to undergo a chemical change
- most elements = somewhat reactive and combine with other materials
- elements in Groups 1 and 17: most reactive
- elements in Group 18: least reactive
Most elements are metals:
metals: elements that conduct electricity, heat well and have a shiny appearance
- can be shaped easily by pounding, bending or being drawn into a long wire
- metals are solids at room temperature (except mercury)
- examples:
- sodium: a metal that is so soft it can be cut with a knife at room temperature
- copper: a metal that has many uses (penny, teapot etc.)
- aluminum: often used for devices that must be strong and light (wheelchair)
- reactive metals:
- metals in Group 1: the alkali metals = very reactive
- sodium and potassium
- often stored in oil to keep them away from air
- when exposed to air = react rapidly with oxygen and water vapor
- ions of these metals (Na+ and K+) = important for life and play an essential role
in the functioning of living cells
- metals in Group 2: the alkaline earth metals = less reactive than the alkali metals but
still more reactive than most other metals
- calcium ions
- an essential part of your diet
- in your bones and teeth
- magnesium: a light, inexpensive metal that is often combined with other metals
when a lightweight material is needed (eg. airplane frames)
- transition metals: elements in the Groups 3-12
- generally less reactive than most other metals
- gold and silver are easily shaped and do not react easily = have been used for
thousands of years to make jewelry and coins
- ancient artifacts made of transition metals = unchanged since time made
- among these metals are some of the earliest known elements
- copper, gold, silver, iron
- examples
- dimes and quarters = made of copper and nickel
- pennies = made of zinc with a coating copper
- transition metal ions = found in foods
- particularly important to industry (because of their properties)
- iron = main part of steel: a material used for bridges and buildings
- copper = make up water pipes and most electric wires and many other electrical
devices
- important for modern technology
- tungsten = in tiny coil of wire inside incandescent light bulbs
- platinum = in the catalytic converters that reduce pollution from automobile engines
- alloys = for many applications, two or more metals are combined to form alloys
- can be stronger, less likely to corrode, or easier to shape than pure metals
- steel (stronger than the pure iron it contains) = often includes other transition
metals - eg. nickel, chromium, or manganese
- brass (alloy of copper and zinc) = stronger than either metal alone
- jewelry (alloy of silver and copper) = stronger than pure silver
- rare earth elements: elements in the top row of the two rows of metals that are usually
shown outside the main body of the periodic table
- often referred to as lanthanides (because they follow the element lanthanum (La) on the
table)
- called rare earth elements because scientists once thought that they were available only
in tiny amounts in Earth’s crust
- scientist learned that the rare earth elements were actually not so rare at all, but only
hard to isolate in pure form
- more and more uses are being found for the rare earth elements
- europium (Eu) = used as a coating for some television tubes
- praseodymium (Pr) = provides a protective coating against harmful radiation in a
welder’s helmet
Nonmetals and metalloids have a wide range of properties: halogens, noble gases, metalloids:
- nonmetals: elements to the right side of the periodic table
- properties
- tend to be the opposite of those of metals
- also tend to vary more from element to element than the properties of the metals do
- many are gases at room temperature (bromine is a liquid)
- solid nonmetals = often have dull surfaces and cannot be shaped by hammering or
drawing into wires
- nonmetals are generally poor conductors or heat and electric current
- examples
- main components of air = nonmetals elements nitrogen and oxygen
- nitrogen = fairly unreactive element
- oxygen = reacts easily to form compounds with many other elements (eg.
burning and rusting are two familiar types of reactions involving oxygen)
- carbon
- compounds containing carbon = essential to living things
- two forms of the elements = graphite (soft, slippery black material) and
diamond (hard crystal)
- sulfur = a bright yellow powder that can be mined from deposits of the pure element
- halogens: elements in Group 17 (from Greek words meaning “forming salts”)
- very reactive nonmetals that easily form compounds called salts with many metals
- because they are so reactive, halogens are often used to kill harmful
microorganisms
- ex: chlorine
- used to clean drinking water
- used prevent the growth of algae in swimming pools
iodine
- solutions containing iodine are often used in hospitals and doctors’
offices to kill germs on skin
- noble gases: Group 18
- called the noble or inert gases because = they almost never react with other
elements
- noble gases produce the light for many signs
- examples:
- argon gas: makes up one percent of the atmosphere (other noble gases are
found in the atmosphere in smaller amounts)
- placed in tungsten filament light bulbs because it will not react with the hot
filament
- colorful lights = made by passing an electric current through tubes filled with
neon, krypton, xenon or argon gas
- metalloids: elements that have the properties of both metals and nonmetals
- in the periodic table, they lie on either side of a zigzag line separating metals from
nonmetals
- most common metalloid = silicon
- silicon atoms are the second most common atoms in Earth’s crust
- found in sand
- found in computer microchips
- metalloids often make up the semiconductors found in electron devices
- semiconductors = special materials that conduct electricity under some
conditions and not under others
- silicon, gallium and geranium = three semiconductors used in computer
chips
(don't worry about radioactivity and half-lifes yet)
SEPUP Chapters:
15: Families of Elements:
Element Cards provide the following information about an element:
• Element symbol
• Element name
• Whether the element is a metal or nonmetal
• Whether the element is solid, liquid, or gas at room temperature
• Color
• Atomic mass: the mass of the smallest particle (an atom) of the
element
• Reactivity: how likely the element is to react chemically with other
elements
• Number of bonds to hydrogen: the number of hydrogen atoms that
usually combine chemically with this element when they react
16: Elements and the Periodic Table:
17: Modeling Molecules:
holes = represent the binding sites
sticks = represent the bonds
Vocabulary List:
Atomic mass: the average mass of all the isotopes of an element
Atomic mass number: the number of protons and neutrons in the nucleus (the mass of the atom
/ the mass of the nucleus)
Periodic table: A tabular arrangement of the elements according to their atomic numbers so that
elements with similar properties are in the same column
Group: a vertical column in the periodic table = elements in a group share similar properties
Period: a horizontal row in the periodic table = properties of elements change in a predictable
way from one end of a period to the other
Family: used to describe elements that share certain characteristics—not only in terms of
observable behavior, but also with regard to atomic structure (electron configuration)
Reactive: how likely an element is to undergo a chemical change (least reactive elements are
the noble gases in Group 18. The most reactive metals are in the two columns to the far left of
the periodic table. The most reactive nonmetals are in the halogen family in Group 17.)
Metals: elements that conduct electricity, are shiny and heat well (reactive metals, transition
metals, rare earth elements)
Nonmetals: elements with properties the opposite of metals
Metalloids: elements with properties between metals and nonmetals
Element: a substance that cannot be broken down into a simpler substance by ordinary chemical
changes (heating it or causing it to react with other chemicals). An element consists of atoms of
only one type.
Chemical formula: a shorthand way to identify the kind and number of atoms that make up a
compound
Compound: a substance made up of two or more different types of atoms bonded together
Molecule: a particle made when two or more atoms bond together chemically, or combine (can
be a molecule of an element and a compound)
Atom: the smallest particle of an element that has the chemical properties of that element
Chemical bond: an attraction between atoms brought about by a sharing of electrons or a
complete transfer of electrons
Double-bond: a bond in which two pairs of electrons are shared between two atoms
Triple-bond: a bond in which three pairs of electrons are shared between two atoms
Transition metals: elements in the Groups 3-12
Valence shell: the outer most energy level of an atom (the valence shell of all elements always
have 8 spaces) (elements in Group 18 always fill 8 spaces in the valence shell)
Energy level: any of the discrete stable energies that a quantum mechanical system (such as the
electrons of an atom) can have (The energy levels around the nucleus of an atom is a spread out
cloud around the nucleus. Electrons can jump energy levels and never stay in one place.)
Bohr model: depicts the atom as a small, positively charged nucleus surrounded by electrons
that travel in circular orbits around the nucleus (rings around the nucleus represent the energy
levels and number electrons). (Not accurate because it has rings, shows an orbit and is twodimensional.)
Mendeleev: In 1869 the Russian scientist Dmitri Mendeleev developed the ideas that led to the
modern periodic table. Mendeleev published the first version of a table of the 63 elements known
at the time. He collected information on the properties of those 63 elements and grouped them
using data that many other scientists had collected about the properties of each of the elements.
When he arranged the elements according to their atomic masses and their physical and chemical
properties, he noticed that there was a repeating—or periodic—pattern. He predicted that there
were more elements that would fit into gaps in his chart, the first version of what came to be
known as a periodic table. He even used the patterns in the table to predict the properties of new
elements. Other scientists used Mendeleev’s ideas and built on them to identify the elements he
predicted. Later scientists found many more elements that follow the patterns he found.
Electron configuration: a form of notation which shows how the electrons are distributed
among the various atomic orbital and energy levels (2, 8, 8)