What would you find in the nucleus of an atom?

An electron has what charge?

What is an element?

Define matter:

What does the atomic number correspond to?

What makes up the atomic mass?

What is a valence electron?

What main types of bonds are there?

What is the pH scale?

Matter, Atoms, and thePeriodic Table

What is Matter?• Matter is defined as anything that

has mass and volume.

– Mass is the amount of matter in an object.

– Volume is the amount of space that an object takes up.

ATOMSATOMS

Atoms• Atoms are the building blocks of all

matter.

• “A-” means “cannot” & “-tomos” means “cut”

• Elements are types of matter that contain only one type of atom.

–Examples of elements: hydrogen, carbon, and oxygen

The Structure of AtomsAtom are composed of a nucleus orbited by electrons.

The nucleus contains protons and neutrons.

Nucleus

Electron

Orbitals

SO…Protons & Electrons attract to one another - this keeps the electrons in orbit around the

nucleus

THE NUCLEUS ELECTRONS

Protons

Outer electrons are known as valence electrons.

Valence electrons are available in bonding with other atoms.

ELEMENT = only made of ONE type of ATOM!!

Valence Electrons• The last energy level holds the valence

electrons.

• The column, or group, on the periodic table indicates the number of valence electrons an element contains.

• The number of valence electrons determines an atom’s bonding properties.– 8 valence electrons = Noble Gases

• Lewis Dot Structures Lewis Dot Structures

Putting Elements Together

• If a sample of matter contains two or more elements chemically combined in a certain ratio, it is called a compound.– Examples: water (H2O), salt (NaCl), and glucose (sugar)

C6H12O6

• Compounds have properties that are different from the elements it contains.

Chemical BondingChemical BondingChemical bonding allows atoms and

molecules to “stick” together.

Types of Chemical Bonding

• Covalent Bonding – Atoms share electrons.

• Ionic Bonding – Atoms gain or lose electrons to form charge particles called ions. Ions then bond together because opposite charges attract.

• Hydrogen Bonding – Molecules stick together because certain parts of them are charged. The oppositely charged parts stick together.

STRONG

WEAK

Molecule = covalent bonds Water molecules attract by hydrogen bonds

Ionic bonds form between metals and non-metals,

In naming simple ionic compounds, the metal is always first, the non-metal second (ie. sodium chloride),

Ionic compounds dissolve easily in water and other polar solvents,

In solution, ionic compounds easily conduct electricity,

Ionic compounds tend to form crystalline solids with high melting temperatures.

Na Cl Na+ Cl- (salt)

Knowing about the structure of atoms can help us understand the functions of certain elements in living things.

Water• Importance of water:

1. Water molecules are polar• Electronegativity

2. Water molecules are cohesive• Hydrogen bonds

3. Water has a high-temperature stabilizing capacity• Common boiling points:

• Methanol 64.7 ºC

• Diethyl ether 35 ºC

• Water 100 ºC

4. Water is the universal solvent• Spheres of hydration

• Hydrophobic vs. hydrophilic

What does pH measure?

H2O H+ + OH-

water Hydrogen ion

Hydroxide ion

pH• Hydrogen ion (H+) is the most reactive ion in

nature• pH scale is the measure of the concentration of

H+ ions in a solution

pH• pH scale ranges from 0 to 14• pH of a solution decreases with acidity• Each step on the pH scale represents a factor of 10

– A solution with a pH of 5 has 10 times more H+ ions than a solution with a pH of 6

Acids and Bases• An acid is any compound that forms H+ ions

when it is dissolved in water to form a solution– Acids have pH values below 7below 7

• A base is a compound that forms hydroxide ions (OH-) in solution– Bases have pH values above 7above 7