Download chapter 2 notes: take home message

CHAPTER 2 NOTES: TAKE HOME MESSAGE
SECTION 1
*Proton: + charge: inside nucleus
*Neutron: O charge: inside nucleus
*Electron: - charge: found in spheres/clouds/shells outside nucleus
*Protons always equal the number of electrons: making the charges balance and
giving the atom an overall neutral charge
*Electrons with lower energy usually move in the space nearer to the nucleus
*Electrons with higher energy usually move in the space farthest away from
nucleus.
*Mass: a proton and a neutron have about equal mass and together they make up
nearly all of the mass of an atom. Mass = protons + neutrons. Both are located in
nucleus
*Mass is actually the average mass of all the isotopes of that element
*To find number of neutrons: Mass - # of protons = # of neutrons
*Each element consists of atoms that differ from atoms of another element:
EACH ELEMENT CAN BE IDENTIFIED BY THE NUMBER OF PROTONS IN THE
NUCLEUS: ATOMIC NUMBER
*Isotopes: all atoms have the same number of protons but their number of
neutrons can vary: for example
Carbon: Atomic number 6: has 6 protons, 6 neutrons
Carbon-14 (C14): Atomic number 6: 6 protons, 8 neutrons
*So an ISOTOPE is an atom with the same number of protons but with a different
number of neutrons
SECTION 2:
*Mendeleev was a Russian scientist who discovered a set of patterns that applied
to all elements: created first periodic table.
*He used information such as: melting point, density, color, atomic mass to
determine the patterns
*He noticed this pattern of properties when he arranged the elements in order of
atomic mass: pattern of properties repeated themselves: left blanks in spaces
where similar elements did not group exactly right.
*Since the early 1900s when scientists discovered a way to measure the positive
charge on the nucleus, the PERIODIC TABLE has been arranged by atomic number
*Mugshot: each square on periodic table which represents an element: tells info
such as atomic number: chemical symbol, name, atomic mass
Organizing periodic table:
*Rows: horizontal: properties of an element can be predicted as you go across
the period:
*From left to right, elements go from highly reactive metals, relatively
unreactive metals, metalloids, non metals and very unreactive gases
*Rows tell the number of electron shells as well as the number of electrons in
each shell.
*Groups: vertical columns also known as families: numbered from 1-18
*Groups tell similar properties and characteristics: also tell the number of
valence electrons
SECTION 3.
Physical Properties of Metals:
shininess
malleability
ductile
* conductivity: the ability of an object to transfer heat and electricity to
another object: Most metals are good conductors
few metals are magnets or are attracted to magnets and can be made into
magnets, iron, cobalt and nickel
*Chemical Properties:
* Reactivity: the ease and speed with which an element combines/reacts with
other elements and compounds.
* Reactivity is determined by the element’s tendency to give up an electron to
other atoms Example: Na reacts strongly when exposed to air or water: Other
metals such as Iron react slowly to oxygen in the air: forming iron oxide or rust:
*Destruction of a metal through this process is called corrosion
*Alkali Metals: Group 1: they are so reactive because they always lose an
electron: never found as uncombined elements in nature: Na, K most important
*Alkaline Earth Metals: Group 2: not quite as reactive as group 1 but more
reactive than most other metals: they lose two electrons: Mg, Ca most common
*Transition metals: groups 3-12 all are good conductors: many form colorful
compounds
*Lanthanides and Actinides: two rows of elements placed below main part of table
simply for convenience: high conductivity: combine with other metals = alloys
*Synthetic elements: >92: not found naturally on Earth: synthesized when nuclear
particles are forced to crash into each other in a particle accelerator.
*Particle accelerators move atomic nuclei faster and faster until they have
reached very high speeds: if fast enough, the particles can sometimes combine
into a single nuclei.
SECTION 4:
*Life on Earth depends on the non metals: ALL LIVING THINGS ARE MADE
FROM COMPOUNDS OF CARBON.
*Living things breath air which contains mainly N & O2
*Water is an essential compound in living cells, H & O
*Physical properties of NON METALS:
poor conductors of electricity and heat
dull, brittle
lower densities
*Chemical Properties:
readily form compounds: Flourine is most reactive element known
Group 18: NOBLE GASES: Hardly ever form compounds: Valence Electrons are
stable at 8
*NON METALS USUALLY GAIN OR SHARE AN ELECTRON
*METAL AND NON METAL REACTIONS: ELECTRON MOVES FROM METAL TO
NON METAL
*NON METALS WITH NON METALS SHARE ELECTRONS
*Diatomic molecules: exists in the form of two atoms O2, N2
METALLOIDS:
*have some characteristics of both metals and non metals
*all are solid at room temperature
*brittle, hard, somewhat reactive
*MOST USEFUL PROPERTY IS THEIR VARYING ABILITY TO CONDUCT
ELECTRICITY: USED AS SEMI CONDUCTORS: computer chips, transistors and
lasers