2.1 Matter

OBJECTIVES:

• Identify elements.

• Particles that make up atoms.

• Describe compounds & how they are formed.

• Identify different chemical bonds.

KEY TERMS:

• Element

• Isotope

• Compound

• Ion

• Chemical bond

• Ionic bond

• Covalent bond

• Metallic bond

Organization of the Periodic Table

• PERIODIC LAW: elements arranged in order of increasing atomic number (similarities in their

properties that occur in a regular pattern).

Periodic means “repeating” pattern.

• GROUP (FAMILY): vertical column.

• PERIOD: horizontal row.

Noble Gases

Periodic Key

6

CCarbon

12.011

Atomic number (Z)

Symbol

Element’s name

Atomic Mass (A)

# of protons = Atomic Number

# of electrons = # of protons (in a neutral atom)

# of neutrons = Atomic Mass – Atomic Number

• Atoms - positively charged

nucleus (protons and

neutrons)surrounded by an

electron cloud.

– Nucleus (99% of atom’s mass).

• Smallest particle of an element.

• Isotopes - same # of protons, different # of neutrons.

Isotopes

IONS

• Many are radioactive

- emit energy & particles.

•Have a charge – came # protons, different # of electrons

•Ionization: process of adding or removing electrons from an atom.

•Becomes either positive (cation) or negative (anion)

Compounds1. Two or more elements (H2O).

2. Properties are different than the individual elements

(Na metal is explosive & Cl gas is deadly, yet NaCl is benign salt!)3. Compounds that occur naturally in nature are called minerals

VALENCE ELECTRONS

• Valence Electrons = Electrons in the

outermost energy level

• They determine how an atom will act in a

chemical reaction.

• Atoms with equal numbers of valence

electrons have similar properties.

• Octet rule: Atoms want 8 electrons in their outer shell.

• Atoms will react and form bonds in a way that allows them to achieve the electron structure of a noble gas (8 electrons in outer shell)

BondsFluorite is an ionic compound that forms

when calcium reacts with fluorine.

1) Ionic - electrons transferred. (opposite

charges attract)

2) Covalent - electrons shared. Ex: Water

• Chemical bonds occur when the outer energy level of an atom is not full (doesn’t have 8 valence electrons)

3) Metallic - attraction between positively

charged metal ions & surrounding electrons.

- Why do metals conduct electricity?

Ex: Bronze = Tin + Copper (Sn + Cu)

Electrons are free to move around

from one atom to another.

Ex: NaCl

Bonding Summary

Type of

Bond

Atom

Types

Involved

Example

Ionic Metal + Non-

Metal

NaCl

Covalent Non-Metal +

Non-Metal

H2O

Metallic Metal + Metal Copper

Carbon-12 and Carbon-14 are:

a) isomers

b) isotopes

c) different elements

Isotopes are atoms of the same element with different numbers of neutrons, therefore different atomic masses.

Carbon-14 is used in radioactive dating, carbon-12 has a more stable nucleus, therefore isn’t used in this capacity.

What part of the atom is much smaller than the atom, yet contains most of the mass?

a) the nucleus

b) the electron cloud

While its diameter is very small compared to that of the entire atom, 99% of the mass of an atom comes from the

protons & neutrons in the nucleus.

Not drawn to scale