JC Science - Structure of the atom

Atom

The smallest particle of an element that still has the properties of that element.

Molecule

When 2 or more atoms join together

Element

Substance made of 1 type of atom

Compound

2 or more different substance that are chemically combined

Mixtures

2 or more different substances that mingle but don't chemically combine

Why is it important to know the structure of the atom

-Tells us whether they are a metal or gas etc
-We can predict how they'll react to make a compound

Subatomic particles

-What atoms are made of
-Protons, neutrons, electrons

What are atoms made of?

-Protons
-Neutrons
-Electrons
-Empty space

Diagram of an atom

a.m.u.

atomic mass unit

Protons (location, mass, charge)

-Location: nucleus
-Mass: 1 a.m.u
-Charge: +1

Neutrons (location, mass, charge)

-Location: nucleus
-Mass: 1 a.m.u
-Charge: 0

Electrons (location, mass, charge)

-Location: electron cloud
-Mass: 1/1836 a.m.u
-Charge: -1

Why is the atom neutral overall

There is an equal number of positive protons + negative electrons so their charges balance

Atomic number

-The number of protons
-The number of electrons
-Always the smaller number

Mass number

-Number of protons + neutrons combined
-Always bigger

How do you find the number of neutrons?

mass number - atomic number

Number of Protons

the same as the Atomic number
.

muber of elecetrons

Same as atomic number

number of Neutrons

Mass No. - Atomic no

Isotopes

-Atoms of the same element that have different numbers of neutrons in the nucleus
-Different mass number

Ions

Atoms that have lost or gained electrons

Anions

Elements which have gained electrons + are negatively charged

Cations

Elements which have lost electrons + are positively charged

Niels Bohr

-He designed a model for the atom
-He said the electron cloud was divided into shells

Electron shells (1 to 3)

1: max 2
2: max 8
3: max 8

Electron cloud

The space around the nucleus where electrons are held

What are electron shells

Energy levels of electrons

How does an element get a full outer shell

-Less than 4 take them away
-More than 4 then add up to 8
-4: add or take away

What happens if the number of protons in an atom changes?

It becomes a different element

What happens if the number of neutrons in an atom changes?

It does not become a different element. It is an isotope

What happens if the number of electrons in an atom changes?

It does not become a different element. It is an ion

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