Chemical Fundamentals Review

• Living things are composed of matter.

• Matter has mass, occupies space.

• Atoms composed of: – Small nucleus

• Proton (positive charge)• Neutron (no charge)

– Orbited by• Electrons in arranged in shells

(negative charge)

What is the PERIODIC TABLE?

o Shows all known elements in the universe.

o Organizes the elements by chemical properties.

How do you read the PERIODIC TABLE?

What is the ATOMIC NUMBER?

o The number of protons found in the nucleus of an atom

Oro The number of electrons

surrounding the nucleus of an atom.

What is the SYMBOL?

oAn abbreviation of the element name.

What is the ATOMIC WEIGHT?

oThe number of protons and neutrons in the nucleus of an atom.

How do I find the number of protons, electrons, and neutrons in an element using

the periodic table?

o # of PROTONS = ATOMIC NUMBER

o # of ELECTRONS = ATOMIC NUMBER

o # of NEUTRONS = ATOMIC _ ATOMIC WEIGHT NUMBER

Example

• Atomic Mass – 12• Atomic Number - 6• Protons (6)• Electrons (6)• Neutrons (12-6 = 6)

Bohr Rutherford Diagrams

1. Write how many protons and neutrons are in the nucleus.

2. Draw electrons in rings (energy shells) around the nucleus.

Ex. Fluorine 19 F9

9p+10 n

Bohr- Rutherford Diagrams

1. Write the # of protons and neutrons in the nucleus.

2. The 1st electron energy shell has a maximum of 2 electrons.

3. The 2nd electron energy shell has a maximum of 8 electrons.

4. The 3rd electron energy shell has a maximum of 8 electrons.

18p+

22n0

Argon

Why are Electrons so Important?

The chemical behaviour of an atom depends mostly on the number of electrons in its outermost shell. valence electrons/shell

All atoms with incomplete valence shells are chemically reactive and are responsible for the formation of chemical bonds between atoms.

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons

C would like to N would like toO would like toH would like to

Gain 4 electronsGain 3 electronsGain 2 electronsGain 1 electron

Atoms bond to form compounds

• Compounds are made up of at least 2 different kinds of atoms (e.g., H2O)

• Bonds are formed by the sharing or transfer of electrons

2 Types of Chemical Bonds

Ionic Bonds

Covalent bonds

Ionic Bonds – occur when one atom donates or gives up one or more

electrons- metal and non metal

Ionic Compound ( Na+Cl-) Salt crystals

Opposite charges

attract to form ionic

bonds

Covalent Bonds – involve a sharing of a pair of valence electrons between atoms between two non-metals

Single covalent bond

Double covalent bond

Four single covalent bonds

Two single covalent bonds

2 Types of Covalent Bonds

Polar Covalent Non-polar covalent

Equal sharing of electrons

Unequal sharing of electrons

Determined by the atoms

ELECTRONEGATIVITY

E.g. H2O2

E.g. H2O

Electronegativity•The measure of an atom’s attraction for additional electrons

•Polar Covalent Bond - unequal sharing of electrons between two atoms with different electronegativity results.

•Non-Polar Covalent Bond – equal sharing of electrons between two atoms.

Electronegativity = Stronger pull of shared electrons

The electronegativity difference (∆En) is the difference in electronegativity number between two atoms participating in a covalent bond.

Electronegativity Differences

Most Biological compounds contain: Carbon, Oxygen, Hydrogen, and NitrogenOxygen and Nitrogen form polar bonds with atoms of most other elementsCarbon and Hydrogen bonds are generally considered non-polar

Molecular Polarity• Depends on – Distribution of charges – Molecular shape

• Symmetrical molecular shapes produce non-polar molecules (whether bonds are polar or not)

• Asymmetrical molecular shapes produce polar molecules

• Balanced charges produce non-polar molecules

• Non-balanced charges produce polar molecules

Polar Molecules• Align themselves

to other polar molecules

• Soluble in water

• Exclude non-polar molecules (oils and fats)

VSEPR• Valence shell electron pair repulsion

• Electrons repel one another forming the shape of the molecule

• Includes both bonded electron pairs and non-bonding electron pairs (lone pairs)

VSEPR