2.1 Nature of Matter

Atom – atomos – “unable to cut”

- basic unit of matter which consists of 3 SUBatomic particle.

Proton

• Location: in the nucleus (center)

• Mass: 1 amu (atomic mass unit)

• Charge: Positive (+1)

Neutrons• Location: in the nucleus

• Mass: 1 amu

• Charge: no charge (neutral)

Electrons• Location: outside of nucleus in orbitals

(electron clouds, energy levels)

• Mass: nearly 0 amu

• Charge: Negative (-1)

Element• Def – a pure substance that consists entirely

of one type of atom.

• Ex – Gold Rutherford's Experiment: Nuclear Atom

Chemical Symbols

6

C12.011

1 – 2 letter chemical symbol

Atomic Number

Atomic Mass

Atomic Number – the number of protons found in the atom

Atomic Mass – the total number of neutrons and protons in the atom. (Units: amu)

Try These

11

Na23

How many protons? 11

How many neutrons? 12

Element Name? Sodium

30

Zn65.5

How many protons?

How many neutrons?

Element Name?

30

35 - 36

Zinc

Isotopes

Def: atoms of an element that have different number of neutrons

• All isotopes have the same chemical properties

Radioactive Isotopes• Def: isotopes that have unstable nuclei that become stable by releasing radiation

– Uses of Radioactive Isotopes• Determine the age of rocks because the nuclei break down at a constant rate.• Treat Cancer

Compounds

Def: a substance formed by the chemical combination of two or more elements in definite proportions

NaCl - Salt H2O - Water C6H12O6 - Glucose

Forming Chemical Compounds

Ionic Bonds – a bond formed when electrons are transferred from one atom to another.– Ions: atoms of the same element that have lost

or gained an electron.

– 2-8-8(18) Rule: Elements want to fill their outer shell by gaining or losing electrons.

Valence Electrons

Valence Electrons: Electrons in the outermost shell of an atom.

Ionic Bonding

Covalent BondsDef: A chemical bond that forms when

electrons are shared between atoms.

Think about Hydrogen

Animation

Molecule: the smallest unit of most compounds.

Covalent BondsWhy does Carbon usually form covalent bonds, instead of ionic bonds?

Answer – Outer shell is half full.

Van der Waals Forces• Sometimes in covalent bonds the sharing of

electrons is not always equal.

• Slight attraction between slightly charged regions of a nearby molecules.

• A combination of ionic and covalent bonds

TED - Gecko Talk

Exit Slip• Draw two molecules of water attached to

each other, show hydrogen bonds, atoms, and charges.

• Boron is atomic #5 and atomic mass is 11 draw this atom, show all subatomic particles.

• How many electrons and protons are in

Cu 2+ (ion of copper) Atm. #=29

Exit Slip 9/27• List at least three unique properties of water.

• Why would we consider protons to be an atoms identity and electrons to be like the personality of an atom?

• Can you explain why one side of a water molecule is slightly positive and the other side is slightly negative?