Basic Chemistry

What is Matter? Matter – the substance of which any physical object is composed States of Matter: Solid Liquid Gas Controlling factors: Temperature Pressure Examples: Gold Mercury Oxygen solid liquid gas

The stuff that makes up all matter The make-up of solid matter on Earth: Atoms  Elements  Compounds  Minerals  Rocks (smallest) (largest)

Element: Periodic Table Fundamental building block Smallest matter that can’t be broken down Periodic Table Rows=periods Columns=groups; elements of a group have similar properties Non-metals, metals, and metalloids

Periodic Table of Elements

Atomic Structure Atoms: Stuff that builds elements Atoms  Elements  Compounds  Minerals  Rocks (smallest) (largest) Atoms: Stuff that builds elements Smallest particle that uniquely defines an element Made of subatomic particles: protons, neutrons, electrons

Atomic Structure Particles that make up an atom: Protons: positive (+) charge Neutrons: no charge Electrons: negative (-) charge, smallest of the subatomic particles Protons + neutrons define the nucleus of an atom. Layers of electrons that orbit around the nucleus are called orbitals or energy-level shells.

Subatomic Particles equal in a neutral atom Atomic Number NUCLEUS ELECTRONS equal in a neutral atom PROTONS NEUTRONS NEGATIVE CHARGE Atomic Number equals the # of... POSITIVE CHARGE NEUTRAL CHARGE Most of the atom’s mass.

Atomic Structure

Periodic Table of Elements Atomic Number (# of protons) Mass number = # protons + # neutrons YES These are called isotopes. Example: (Carbon) 12C 13C 14C Can atoms of the same element have different mass numbers? Atomic weight = # protons + average # neutrons

Atomic Structure Atoms of the same element: have the same number of protons (i.e., same atomic number) can have different numbers of neutrons (referred to as isotopes) can have different numbers of electrons Ion – an atom that has gained or lost an electron

Mass # Atomic # Nuclear symbol: Hyphen notation: carbon-12 Isotopes Atoms of the same element with different mass numbers. Nuclear symbol: Mass # Atomic # Hyphen notation: carbon-12

Isotopes © Addison-Wesley Publishing Company, Inc.

17 37 20 Isotopes Chlorine-37 atomic #: mass #: # of protons: # of electrons: # of neutrons: 17 37 20

Atomic Structure Sodium atom Chlorine atom loses an electron (becomes positively charged) Chlorine atom gains an electron (becomes negatively charged)

Atomic Structure: IONS Ion: atom that has gained or lost an electron Types of IONS: CATIONS – a loss of electrons, resulting in a positive (+) charge ANIONS – a gain of electrons, resulting in a negative (-) charge Examples: Na+ (cation) Cl – (anion) NaCl (table salt) chemical compound

Compounds Definition: Examples: NaCl H2O Atoms  Elements  Compounds  Minerals  Rocks (smallest) (largest) Definition: A chemical compound consists of elements that combine in a specific ratio. Examples: NaCl H2O The smallest quantity of a compound is called a molecule. Molecules are held together by chemical bonding.

What is a chemical bond? An attractive force between the nuclei and valence electrons of different atoms that binds them together Formation of a compound by combining two or more elements Manner in which electrons are distributed In bonded atoms, electrons may be lost, gained, or shared Bonds form in order to… decrease potential energy (PE) increase stability

Ionic Bonds Ionic Bonds are formed by the TRANSFER of electrons Moderately strong bond What constitutes an ion? Positive or negative charge Cation or anion Opposites attract Cations will attract anions Anions will attract cations Bonding ALWAYS takes place in the valence shell between valence electrons

Ionic Bonding Na+ Cl–

What makes an ionic bond? Must include a metal + a non-metal Metal = cation Non metal = anion Anion “takes” electron from cation Cation is willing to give it away, to lower an energy level Anion is looking to fulfill the octet rule For this reason – group I and II metals “LOVE” group 17 non-metals (halogens) Creates a salt

Covalent Bonds Compounds that are made of molecules Bonds that are formed by SHARING electrons Electrons are shared from the valence shell, still want it full! Generally STRONGEST Bonds Non-metal + non-metal (diamond, pure C)

What makes a Covalent Bond Non-metal + non-metal Some examples below Can share more than one pair of electrons single bond shares one pair electrons double bond shares two pairs electrons triple bond shares three pairs electrons

Metallic Bonds Metal + metal Generally weaker, less common than other bonds Electrons drift around from atom to atom Electrons are free to move from atom to atom This is why they are good conductors of electricity Gold, copper, silver

Van der Waals Van der Waals bonding: sheets of covalently bonded atoms held together by weak electrostatic forces very weak bonds examples: graphite, mica

Van der Waals  metallic  ionic  covalent Bond Strength Van der Waals  metallic  ionic  covalent (weakest) (strongest)