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MATTER: Atomic Structure Elements The elements, alone or in combinations, make up our bodies, our world, our sun, and in fact, the entire universe. Definition: a substance that cannot be broken down into a simpler substance by chemical means.. The most abundant element in the earth’s crust is oxygen. 90 elements occur naturally on earth. The others have been created in labs. What is an atom? The smallest unit of an element They can’t be broken down Atoms are so small we could fit over a million atoms inside this period . Subatomic Particles Protons and electrons are the only particles that have a charge. PROTONS have a (+) positive charge (in nucleus) ELECTRONS have a (-) negative charge NEUTONS have no charge (in nucleus) Protons and neutrons have essentially the same mass. The mass of an electron is so small we ignore it. The Nucleus The protons and neutrons packed closely together make up the nucleus Located in the CENTER of the atom It is Positively charged Makes up most of the mass but not volume EXAMPLE: Gumdrop/Football stadium Electron Cloud Electrons move inside this region Since opposite charges attract each other The negative (electrons) are attracted to the positively charged nucleus Atomic Number The number of protons in the nucleus is called the atomic number. No two elements, have the same number of protons. Bohr Model of Hydrogen Atom Wave Model Atomic Number Atomic Mass The mass of an atom in atomic mass units (amu) is the total number of protons and neutrons in the atom. Atomic Mass Atomic Mass refers to the “weight” of the atom. It is derived at by adding the number of protons with the number of neutrons. HOW TO READ THE PERIODIC TABLE How to find protons: The number of protons equals the atomic number How to find neutrons: 1. Find the atomic weight of the element 2. Find the number of protons of the element 3. Subtract the number of protons from the atomic weight of the element How to find the electrons and rings: 1. Find the electrons in each ring at the bottom of your element 2. The number of electrons on each ring is given from left to right 3. The first number on the left represents the first ring outside of the nucleus Introduction The periodic table is made up of rows of elements and columns. An element is identified by its chemical symbol. The number above the symbol is the atomic number The number below the symbol is the rounded atomic weight of the element. A row is called a period A column is called a group Names of Elements The first 103 elements have internationally accepted names, which are derived from: The compound or substance in which the element was discovered An unusual or identifying property of the element Places, cities, and countries Famous scientists Greek mythology Astronomical objects. Dmitri Mendeleev Russian scientist born in Siberia in 1834, is known as the father of the periodic table of the elements. The periodic table of the elements is an important tool used by students and chemists around the world to help them understand and simplify the often complex world of chemical reactions. Not only did Mendeleev arrange the periodic table of the elements, he also wrote and published a 2 volume chemistry book entitled Principles of Chemistry as there was no thorough chemistry textbook at the time. The Big Task Mendeleev set out to identify a pattern in the elements. Mendeleev looked at many pieces of evidence and made an important observation that some elements have similar chemical and physical properties. Mendeleev's hunch was that these similarities were the key to unlocking the hidden pattern of the elements. Mendeleev then embarked on the tedious task of organizing all known information for every element to help him decipher the pattern. To begin his task, Mendeleev wrote facts about the elements on individual paper cards. On these cards, Mendeleev wrote information such as the elements' melting points, densities, colors, atomic masses (the average mass of one atom of that element), and bonding powers (the number of chemical bonds an element can form). Once Mendeleev's cards were made, he tried arranging them in various ways. Finally, Mendeleev noticed that patterns appeared when the elements were arranged in order of increasing atomic mass. Mendeleev's table was not perfect, however. Arranging the elements by increasing atomic mass left three blank spaces in the table. This first periodic table of the elements was published in 1869. The word "periodic" means that there is a repeating pattern -- that is, the properties of the elements repeat with each row -- or period -- of the table. Amazingly, within 16 years of Mendeleev's first periodic table, chemists had discovered all three of the missing elements (scandium, gallium, and germanium), and their properties were very close to what Mendeleev had predicted. Periodic Table The rows on the periodic chart are periods. The period tells you which shell with the highest energy is being used by that atom. So every atom in the third period aka the third row is using up to the third shell of their shells of electrons. Columns are groups. Elements in the same group have similar chemical properties. Today there are 111 elements recognized by IUPAC (International Union of Pure Applied Chemistry ) Groups These five groups are known by their names. Periodic Table Nonmetals are on the right side of the periodic table (with the exception of H). Periodic Table Metalloids border the stair-step line (with the exception of Al and Po). Periodic Table Metals are on the left side of the chart. Symbols C Cu Carbon Copper All elements have their own unique symbol. It can consist of a single capital letter, or a capital letter and one or two lower case letters. Calculating the # of electrons in each shell In other words, electron shells have a limited capacity for electrons. As you might expect, the farther an electron shell is from the nucleus, the larger it is. You can calculate the total capacity of an electron shell using the formula 2n2, where n equals the number of the electron shell. For example, for the 1st electron shell n = 1 and 2 x 1x1 = 2, telling us that the capacity of the 1st shell is 2 electrons as we have already seen. For the 2nd shell (n = 2) and 2 x 2x2 = 8. For an atom to fill its 2nd electron shell, it would need 10 electrons: 2 to fill the 1st shell and 8 to fill the 2nd. The 3rd shell has a total capacity of 2 x 3x3 = 18 electrons. Shell Number 2 * (the shell number * the shell number) = the maximum number of electrons in this shell. Maximum Number of Electrons in the Shell 1 2 x (1 x 1) = 2 2x1=2 2 2 x (2 x 2) = 8 2x4=8 3 2 x ( 3 x 3) = 18 2 x 9 = 18 4 2 x (4 x 4) = 32 2 x 16 = 32 5 2 x (5 x 5) = 50 2 x 25 = 50 There are five possible shells available to atoms. This diagram shows only three shells, and some atoms, such as the little hydrogen atom, use only the one inner shell. Each of the elements has a different number of the tiny electrons, and a corresponding number of protons. Hydrogen is the smallest, with only one electron. Carbon, nitrogen, and oxygen, are also small, light atoms. Get a white piece of paper Select 4 elements Draw the atomic model for each Element 5: Boron Element 6: Carbon Element 7: Nitrogen Element 8: Oxygen Element 9: Fluorine Element 10: Neon Element 11: Sodium Element 12: Magnesium Element 13: Aluminum Element 14: Silicon Element 15: Phosphorus Element 16: Sulfur Element 17: Chlorine Element 18: Argon HW choose 3 elements Tell me how many protons, neutrons and electrons Draw a diagram of the element and color code it Valence Electrons The number of valence electrons an atom has may also appear in a square. Valence electrons are the electrons in the outer energy level of an atom. These are the electrons that are transferred or shared when atoms bond together. Valence electrons The outer shell electrons that are available for and capable of forming bonds with other atoms. Valence electrons are electrons occupying the outermost energy level. Properties of Metals Metals are good conductors of heat and electricity. Metals are shiny. Metals are ductile (can be stretched into thin wires). Metals are malleable (can be pounded into thin sheets). A chemical property of metal is its reaction with water which results in corrosion. Properties of Non-Metals Sulfur Non-metals are poor conductors of heat and electricity. Non-metals are not ductile or malleable. Solid non-metals are brittle and break easily. They are dull. Many non-metals are gases. Properties of Metalloids Silicon Metalloids (metal-like) have properties of both metals and non-metals. They are solids that can be shiny or dull. They conduct heat and electricity better than nonmetals but not as well as metals. They are ductile and malleable. Hydrogen The hydrogen square sits atop Family IA, but it is not a member of that family. Hydrogen is in a class of its own. It’s a gas at room temperature. It has one proton and one electron in its one and only energy level. Hydrogen only needs 1 electron to fill up its valence shell. Alkali Metals The alkali family is found in the first column of the periodic table. Atoms of the alkali metals have a single electron in their outermost level, in other words, 1 valence electron. They are shiny, have the consistency of clay, and are easily cut with a knife. Alkali Metals They are the most reactive metals. They react violently with water. Alkali metals are never found as free elements in nature. They are always bonded with another element. What does it mean to be reactive? Elements that are reactive bond easily with other elements to make compounds. Some elements are only found in nature bonded with other elements. What makes an element reactive? An incomplete valence electron level. All atoms (except hydrogen) want to have 8 electrons in their very outermost energy level (This is called the rule of octet.) Atoms bond until this level is complete. Atoms with few valence electrons lose them during bonding. Atoms with 6, 7, or 8 valence electrons gain electrons during bonding. Ions When atoms lose or gain electrons, they become ions. Ions are atoms with either extra electrons or missing electrons. A normal atom is called a neutral atom. That term describes an atom with a number of electrons equal to the atomic number. If an atom has the same number of protons and electrons, it is electrically neutral. If electrons are added or removed, the atom (now called an ion) becomes charged Example Sodium (Na) atom has eleven electrons one too many in her outer shell she needs to find another element who will take that extra electron away so she can be complete (filled electrical orbital's) Bring in chlorine (Cl). Chlorine (Cl) will take that electron away and leave her with 10 electrons inside of two filled shells. She is now a happy atom. Now she is an ion and missing one electron. She is now sodium ion (Na+). She has one less electron than your atomic number Now with filled shells. Sodium is a stable atom. LOST one (+) positively charged ion Chlorine GAINED one (-) negatively charged ion What do you do that's so special now? Now that you have given up the electron, you are quite electrically attractive. Other electrically charged atoms (ions) are now looking at you and seeing a good partner to bond with. The Oppositely charged ions attract each other and form an ionic bond Cations are positive ions and are formed by elements on the left side of the periodic chart. Removing electrons from the atom results in a positively charged ion, Anions are negative ions and are formed by elements on the right side of the periodic chart. Adding electrons results in a negatively charged ion BONDIING There are two main types of bonding Electrovalent/ Ionic and Covalent Ionic Bonds = the attractive force between oppositely charged ions that result from the transfer of electrons from one atom to another. If a compound is formed through the transfer of electrons its called Ionic Compound (NaCl) Positive because now the atom is more positively charged it has 11 protons & 10 electrons Negative because now Cl has an extra negative charge and it will make it more negative Covalent Bonds= form when atoms share one or more pairs of electrons. The nucleus of each atom is attracted to the shared electrons & keeps it together Ionic Bonds Ionic compounds (such as NaCl) are generally formed between metals and nonmetals. Chemical Bonding Two types of bonding Ionic bonding Covalent bonding Polar covalent Metallic OPEN PPT on Desktop CHEMBOND Isotopes: Atoms of the same element with different # of neutrons. Isotopes have different numbers of neutrons. 11 C 6 12 C 6 13 C 6 14 C 6 Some isotopes are stable, while others are radioactive—they eventually break down and release particles or energy called radiation. Let's say an atom is missing a neutron or has an extra neutron. That type of atom is called an isotope. An atom is still the same element if it is missing an electron. The same goes for isotopes. They are still the same element. They are just a little different from every other atom of the same element. Elements, Compounds, Mixtures Sodium is an element. Chlorine is an element. When sodium and chlorine bond they make the compound sodium chloride, commonly known as table salt. Compounds have different properties than the elements that make them up. Table salt has different properties than sodium, an explosive metal, and chlorine, a poisonous gas. Dalton’s Postulates 1. Every element is composed of tiny particles called atoms 2. All atoms of a given element are identical 1. Atoms of different elements have different properties 3. Atoms of an element are NOT changed into atoms of another element by chemical processes 1. Matter can neither be created nor destroyed 4. Compounds are formed when atoms of more than one element combine