atoms atoms are the building blocks of all matter. an atom is made up of smaller bits called…...

*Structure of the atom

ATOMSAtoms are the building blocks of all matter.

An atom is made up of smaller bits called…

Name Charge Position MassProtons

Electrons

Neutrons

+ve

-ve

neutral Nucleus

Outside

Nucleus 1

0

1

ELEMENTSAn element is a substance made up of only 1 type of atom. There are about 112 different atom types therefore there are 112 elements. These are shown on the periodic table of the elements.

On the periodic table each atom type has its information. For example…

Atomic no.

Symbol

NameAtomic mass.

PERIODIC TABLE

Any atom can be identified by the atomic no., the symbol or by the name. For instance...

Atomic no.

SymbolName

Name Symbol Atomic No.

Hydrogen

Fe

12

Iron

Magnesium

H

Mg

1

26

The information from the table can also be shown as:

11

5B

WHAT IT MEANSThe Atomic Number:

= number of protons

= number of electrons (as an atom has the same of each)

The Mass Number:

= number of protons + neutrons - why are electrons not included in the mass no?

They have no mass!

So for Boron…

Protons =

Electrons =

Neutrons =

5

5

6

What about Phosphorus?

Protons =

Electrons =

Neutrons =

15

15

16

11

5B

*Learning Check

Select the correct symbol for each:

A. Calcium

1) C 2) Ca 3) CA

B. Sulfur

1) S 2) Sl 3) Su

C. Iron

1) Ir 2) FE 3) Fe

*Learning Check

Select the correct name for each:

A. N

1)neon 2)nitrogen 3)nickel

B. P

1)potassium 2)phlogiston3)phosphorus

C. Ag

1) silver 2)agean 3)gold

ELECTRON ARRANGEMENT

Electrons are very fast moving. They are arranged in shells around the nucleus using the rule 2,8,8.

The first shell fits up to…

The second fits up to…

The third fits up to…

So the electron shell arrangement for 12Mg would be…

2 e

8 e

8 e

2, 8, 2

GROUPS

The columns in the periodic table are called groups. Groups of elements share similar reactivity.

This is because they have the same number of valence electrons.

As you go down a group the reactivity increases.

Group 1 are the alkali metals

properties: good conductors

solid at room temperatures

can be cut with a knife

low densities and melting points

Group 17 are the Halogens

*The rows in the periodic table are called periods.

*Atom’s size decreases from left to right in a given period

*The period tells you the number of energy shells in an atom.

*Periods

*Learning Check

A. Element in Group XVII, Period 4 1) Br 2) Cl 3) Mn

B. Element in Group II, Period 3

1) beryllium 2) magnesium 3) boron