Unit 2 - Chapter 3 Elements, Atoms, Ions

The elements Can we name some? How many are there? Where would you find that information?

Element Symbols Each element has a unique symbol. The first letter is always capitalized if a second letter, it is always lower case Usually the 1 st letter of its name, then the 2nd letter or unique letter. Carbon, Calcium, Cadmium, Californium Some unusual symbols - mostly based on latin roots sodium, potassium, gold, lead, mercury, iron, etc.

Atomic size We can take a chunk of matter and break in apart into smaller and smaller pieces, eventually we would get down to individual atoms. Each piece would behave like the original chunk with all of its properties. The atom is the smallest particle of an element that retains the properties of the element copper atoms lined up would be 1 cm. What would be the diameter of a single copper atom?

Atomic theory - Chpt 3.2 Democritus (ancient greek philosopher) stated that if you broke down matter eventually you would get to the smallest particle of matter that could not be divided (atomos) John Dalton s - Did Chemical Experiments! Things (matter, compounds) always combined in the same proportions SIMPLE WHOLE NUMBER RATIOS Law of Constant Composition - a compound always has the same composition regardless of where it comes from or how it is made Dalton’s Atomic Theory - page 56 of textbook

Dalton’s Atomic Theory pg. 56 Textbook Elements are made of tiny particles - atoms All atoms of an element are identical. Atoms of an element are different from all other elements. Atoms can combined to form compounds. A compound always has the same number and types of atoms. SIMPLE WHOLE NUMBER RATIOS Atoms are not created nor destroyed by chemical reactions, simply rearranged or grouped together differently

Compounds Compound is a distinct substance, that is composed of 2 or more elements, always in the same proportions (whole number ratios) Can we name some? A compound has a unique chemical formula, which indicates which elements and how many are in that particular substance.

Atomic Structure - Chpt 3.3 What is a Model of the atom? How did we get there? Dalton - Chemical Experiments determined atom was indivisible (a solid sphere) Cathode Ray tube experiments by J.J. Thomson (plum pudding model or TODAY maybe chocolate chip ice cream) Gold foil experiment by E. Rutherford (nuclear atom - the marble in the Metrodome)

J.J. Thomson’s Experiment The cathode ray tube discovered was a beam of particles The beam was deflected by magnets changed the gas -> didn’t change beam, changed metal anode -> didn’t change beam Particle was a fundamental particle of all substances! Particle was a part of all atoms!!!! 1st Subatomic particle, so the atom was made of smaller particles JJ Thomsom discovered the electron. Didn’t know about the rest of the atom, so just said it was like Plum Pudding

Rutherford’s Gold foil Experiment Bombarded a thin gold foil with positively charged alpha particles. Looked at flashes of light when film was hit. Most of the particles went straight through 1 out of 20,000 bounced almost directly back Conclusions: Atom is mostly empty space positively charged nucleus with most of the mass

Isotopes Not all atoms of an element are the same! The identity of an atom is determined by the number of protons. Atomic number is the # of protons in an atom, Z. atomic number is found on periodic table! # of protons = # of electrons in neutral atom. Mass number is the sum of the protons + neutrons in the nucleus of the atom, A #of neutrons = Mass number - Atomic number = A - Z Isotopes are atoms of the same element with different numbers of neutrons

Isotope examples For the masses of atoms we use amu (atomic mass unit) - 1 amu is defined as one-twelfth the mass of the carbon- 12 atom. hydrogen-1, hydrogen-2, hydrogen-3 also written 1 H 2 H 3 H A H the number is the mass number, the atom name tells us how many protons! how many protons does hydrogen have? how many neutrons does each isotope have? oxygen-16, oxygen-17, oxygen-18 how many protons and neutrons?

Atomic Mass Atomic mass from periodic table is a weighted average of the stable isotopes found on earth. If we are given the percentage of each isotope and its mass can calculate the atomic mass. Simply multiply the percentage times the mass for each isotope and add up each isotopes contribution to get the atomic mass.

Periodic Table - Chpt 3.4 Write the key terms (pg. 68) in your notebook. The elements were organized into the Periodic Table by Mendeleev in Columns (groups or families) of elements have similar chemical properties He left blank spaces - prediction of previously unknown elements These were found and confirmed his predictions!! 7 periods (rows), 18 groups (columns) alkali metals, alkaline earth metals, halogens, noble gases

Mendeleev’s 1869 Periodic Table

Properties of metals Solid, shiny Conduct electricity Conduct heat Malleable (hammer into shapes) and Ductile (drawn into wires)

Types of elements Metals Non-metals Metalloids (semimetals) - along the staircase - separates the metals from the nonmetals Most elements are considered single atoms, a few are only found as diatomics - two atoms together, H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 hockey stick and puck or B rINClHOF “brinklehof”

Extra Credit - Unit 2 Chapter 3 - pg , # 5, 6, 7, 10, 12, 14, 17, 18, 19, 21, 23, 29, 30, 33, 35, 39, 40, 41, 42, 46, 53, 55