Warm up9-30-08 What part of the atom has a positive charge and where is it found?

the atomWhat is an atom?

What are the parts of an atom?

What is the structure of the atom?

The smallest particle of an element that has the characteristics of that element

protons (p+); neutrons (n); electrons (e-)

Nucleus contains protons & neutrons, electrons circle the nucleus in an electron cloud

n

e-

e-

P+ P

+n

something to think about

• We all know that “opposites attract” and “like charges repel” –SO:

• If electrons are negatively charged and protons are positively charged, why don’t the electrons fall into the nucleus?

?

Niels Bohr proposed a model in which the electrons would stably occupy fixed energy levels around the nucleus, known as orbitals. Each orbital has a limited capacity for electrons.

something to think about

Some elements also have neutrons Neutrons have no chargeThey are in the nuclei of atoms

The element also has the same number of electronsElectrons have negative chargeChange the number of electrons charge the atom

Each element in the Periodic Table has a different number of protons in its nucleusProtons have positive chargeChange the number of protons change elements

e-

Recipe for an atom

P+

n

Atomic number

Atomic weightName

Symbol

Protons = 8 Electrons = 8 16 – 8 = 8 neutrons

# Protons = # Electrons

The electron orbitals

# Neutrons = Atomic Weight – Atomic #

# Protons = # Electrons

# Neutrons = Atomic Weight – Atomic #

Shell structure activity

Carbon = C

Sulfur = S

Neon =Ne

Chlorine = Cl

How many protons and electrons do these elements have?

Draw the electron shell structure for each.

3 protons3 electrons4 neutrons

e

e

e

n

n np

p

p

n

Navigating the Periodic Table

The columns are the “groups”Each group has similar chemical propertiesThe groups are numbered starting with 1 at the leftElements with similar properties have the same

number of electrons in the outermost shell

The rows are the “periods” Each period starts a new shell of electronsThe periods are numbered starting with 1 at the

top

Atoms, Elements and Compounds

Compound: a collection of 2 or more different atoms, bound together. H2O or CO2

Atom: smallest unit of an element

Element: any of more than 100 fundamental substances that consist of atoms of only one kind (C; K; Mg; Ca)

The mighty electron

e

ee

e

e e

6P6P6P6P

6N

Carbon

e

ee

e

e e

6P6P6P12P

12N

e

e

e

e

e

e

e

ee

e

e e

6P6P6P10P

10N

e

e

e

e

neon

magnesium

e

ee

e

e e

6P6P6P17P

17N

e

e

e

e

e

e

e

e

e

ee

chlorine

1734Cl

ee

ee

e

e e

6P6P6P17P

17N

e

e

e

e

e

e

e

e

e

ee

e

ee

e

e e

6P6P6P17P

17N

e

e

e

e

e

e

ee

Cl-

e

ee

e

e e

6P6P6P17P

17N

e

e

e

e

e

ee

e

e e

6P6P6P11P

11N

e

e

e

e

e

Na +Opposites attract

Ionic bond

CHARGE!!!

Ion – an atom with a charge

Cation – an atom with a positive chargeless electrons than protons

Anion – an atom with a negative chargeMore electrons than protons

NaNa++

Cl-

covalent bond: When electrons are SHARED

e

ee

6P6P6P17P

17N

e

e

ee

e

e e6P6P6P8P

8N

e

e

O

1PH 1P He

e

e

e

Molecule – a group of atoms held together by covalent bonds

H 2 O

MOLECULES

Chemical reactions occur when bonds between atoms are formed or broken