What are elements? Element: Substance that cannot be broken down into a simpler form by ordinary chemical means. All matter is made of elements 92 naturally occurring elements on Earth. Elements are made up of atoms. They Might Be Giants

Components of an atom Atoms: Smallest particle of an element that has all characteristics of an element. Nucleus: Center of the atom Protons: “Large”, positively charged particle. Neutrons: “Large”, neutral particle.

Components of an Atom Outside the nucleus: Electrons: Negative charge found outside the nucleus in the electron cloud. 1st energy level: Can hold 2 electrons 2nd energy level: Can hold 8 electrons 3rd energy level: Can hold 18 electrons

There are an equal number of protons & electrons in a neutral atom Atomic Number: Number of protons in the nucleus. This determines what element the atom is! There are an equal number of protons & electrons in a neutral atom *Nucleus has a positive charge* *Atoms have neutral charge*

Atomic Mass: Mass of the nucleus (Number of protons + Number of neutrons) The number of neutrons can vary in an atom, but the protons will always be equal to the atomic number.

Isotope Notation 8 8 Protons Electrons Neutrons Mass # Atomic # 15-8 = 7

How to determine Atomic and Mass #s If you are not given the atomic number, simply look at the periodic table. If you are not given the mass number… If you have protons and neutrons, add them If you don’t have protons and neutrons, take the mass from the periodic table and round to the nearest whole number

Sodium Br Name Symbol Atomic number Mass Number # of Protons # of Neutrons # of electrons Sodium Br

Na 11 22.99 12 Sodium Br Name Symbol Atomic number Mass Number # of Protons # of Neutrons # of electrons Sodium Na 11 22.99 12 Br

Na 11 22.99 12 Br 35 79.90 45 Sodium Bromine Name Symbol Atomic number Mass Number # of Protons # of Neutrons # of electrons Sodium Na 11 22.99 12 Bromine Br 35 79.90 45

Practice How many protons are there in Lithium-7? How many neutrons are there in Lithium-7? How many protons are there in Mg? How many electrons are there in Mg? How many neutrons are there in ? How many neutrons are there in Oxygen-18?

Practice How many protons are there in Lithium-7? 3 How many neutrons are there in Lithium-7? 4 How many protons are there in Mg? 12 How many electrons are there in Mg? 12 How many neutrons are there in ? 11 How many neutrons are there in Oxygen-18? 10

Isotopes Atoms of the same element (same # of protons), but with different numbers of neutrons. Have different mass numbers Isotopes behave the same chemically because they still have the same number of protons and electrons

Isotopes of Neon Protons Electrons Neutrons 10 10 10 10 10 10 10 11 12

Ions So far, we have focused on neutral atoms Which have an equal number of protons and electrons We know the protons are tightly held in the nucleus Held there by nuclear forces

Ions Electrons are scattered outside the nucleus Less restricted and able to change When an atom gains or loses electrons, it is called an ion

Gain Electrons Negative charge Called an anion Ex. Protons Electrons Neutrons

Gain Electrons Negative charge Called an anion Ex. Protons 8 Electrons 10 Neutrons

Lose Electrons Positive charge Called a cation Ex. Protons Electrons Neutrons

Lose Electrons Positive charge Called a cation Ex. Protons 13 10 Neutrons 14

Isotope (of same element) Particle Changed Result Proton Different Element Neutron Isotope (of same element) Electron Ion (of same element)

Normal: Atomic Mass _______ Chlorine has ________ # of protons _________ # of Neutrons _________ # of Electrons Isotope: Atomic Mass 37 ISOTOPE) ________ # of protons _________ # of Neutrons _________ # of Electrons

Normal: Atomic Mass _35.45__ Chlorine has __17____ # of protons ____18___ # of Neutrons ___17____ # of Electrons Isotope: Atomic Mass 37 ___17___ # of protons ___20____ # of Neutrons ____17___ # of Electrons

Atom Bonding Valence electrons: Electrons found in the outermost energy level. Atoms bond with each other according to the number of valence electrons in order to be stable. Stable atom=Outermost electron valence shell is full.

Chemical Bonds Ionic Bonds Covalent Bonds Hydrogen Bonds

Ionic Bonds Electrons are transferred between atoms A metal and a nonmetal Positive & Negative Ions attract each other like magnets.

In a chemical formula, the positive ion is always written before the negative ion Ex: Na+ Cl-

Covalent Bonds Electrons are shared between atoms Both are nonmetals Polar molecule- shares the electrons uneqaully, giving it a + and – side. Nonpolar molecules share equally.

Hydrogen Bonds Weak, intermolecular bonds Formed when the + side of one polar molecule is attracted to the – side of another polar molecule.