Target 2-1 Tuesday, October 10, 2017 Atomic Structure Target 2-1 Tuesday, October 10, 2017

Target 2-1 I can describe the structure of an atom by interpreting the periodic table.

Atoms Atom: smallest unit of matter There are different types of atoms Each different type of atom is a different element

Atoms Most of the atom is empty space Nucleus: center of the atom The nucleus contains almost all of the mass of the atom

Diagram of an Atom Atom Nucleus Empty Space

Subatomic Particles Subatomic = inside an atom Protons Neutrons Positive charge (+) Located in the nucleus Mass of 1 Neutrons Neutral (no charge)

Subatomic Particles Electrons Negative charge Located outside the nucleus (electron cloud) No measurable mass

Diagram of an Atom Nucleus Atom Electrons (in Electron Cloud) (protons and neutrons held together by Strong Force)

Elements Elements are specific types of atoms different elements = different atoms Elements are organized on the Periodic Table

Elements on the Periodic Table 3 Li Lithium 6.941 Atomic Number (whole number) Atomic Symbol (letters) Element Name Atomic Mass (decimal number)

Atomic Number Atomic Number: tells us the number of protons in an atom of that element Same for every atom of an element Same number of protons and electrons + - (overall charge of atom is 0) Ex) 2+ and 2- = 0

Mass Number Mass Number: the total mass of an atom Mass number = # of protons + # of neutrons # of neutrons = Mass Number – # of protons Electrons are not counted in the mass number Two ways to write mass numbers: lithium-7 Li both mean an atom of lithium (Li) with a mass of 7 7

Isotopes Mass number is NOT always the same for every atom of an element Isotopes are atoms of the same element that have different mass numbers Happens because of different # of neutrons Ex) Lithium-7 and Lithium-6 3p, 4n 3p, 3n

Atomic Mass Atomic Mass: is the average mass number of all the isotopes of an element The atomic mass is always a decimal because it’s a calculated average If you are not given a mass number, you can estimate it by rounding the atomic mass to the nearest whole number

Exit Ticket How many p, e, n are there in… Magnesium-25 Fluorine-20 Beryllium