Chemistry - book 1: Atomic Structure

definiton of an atom

The smallest part of an element that can exist

definition of an element

A pure substance made of only one type of atom

definition of a compound

A pure substance made of two or more different atoms chemically bonded together

definition of a molecule

A substance made of more than one atom chemically bonded together, e.g. Cl₂, CH₄, O₂

definition of a mixture

A substance made of more than one substance, not chemically bonded together.

How can we separate a mixture of sand and water?

Filtration.

How can we separate a mixture of liquids with different boiling points?

Fractional distillation

How can we separate a mixture of coloured dyes?

Chromatography

___ The Three subatomic particles

Protons, Neutrons, Electrons

State the relative masses and charges of the subatomic particles

Mass: protons 1, neutrons 1, electrons 0

 

Charge: protons +1, neutrons 0, electrons -1

____ is the plum pudding model of an atom

A ball of positive charge with negative electrons embedded into it.

What did the gold foil experiment (alpha particle scattering) prove?

Atoms have a small, dense nucleus with a positive charge, and are mostly empty space

What did Chadwick discover?

The neutron

What did Bohr’s experiments show?

Electrons are arranged in specific shells or energy levels

What is the atomic number of an atom?

The number of protons in an atom

What is the mass number of an atom?

The number of protons + the number of neutrons in an atom

How are the subatomic particles arranged in an atom?

Protons and neutrons in the nucleus, electrons orbiting the nucleus in shells

Why is the number of electrons in an atom equal to the number of protons?

Protons are positive, and electrons are negative, so their charges cancel out

How many electrons can go in the first shell?

2

How many electrons can go in the second and third shells?

8

What are groups in the periodic table?

The vertical columns, numbered 1,2,3,4,5,6,7,0

What can the group tell you about the electrons in an atom?

The number of electrons in the outer shell. e.g. carbon is in group 4 so has 4 electrons in the outer shell.

What are periods in the periodic table?

The horizontal rows in the periodic table

What can the period tell you about the electrons in an atom?

The number of electron shells an atom has.

e.g. carbon is in the second period so has two shells

Why do atoms have no overall charge?

Protons are positive, and electrons are negative, and the number of electrons and protons are equal

Approximately how large are atoms?

Radius is about 0.1nm (1 x 10^-10 m)

How large is the nucleus compared to the whole atom?

About 1/10,000 the size (1 x 10^-14 m)

What are isotopes?

·        Atoms of the same element with the same number of protons

but a different number of neutrons

What is the relative atomic mass (A_r) of an element?

An average value for the mass number that takes into account the different isotopes of the element

In the modern periodic table, how are the elements arranged?

By increasing atomic (proton) number

 

(and in groups according to similar chemical properties)

Why do elements in the same group have similar chemical properties?

Because they have the same number of electrons in their outer shell

Before the discovery of protons, neutrons and electrons how did scientists organise the elements?

By their atomic weight

Why did Mendeleev leave gaps in his periodic table?

For elements that had not yet been discovered

Why did Mendeleev swap the order of some elements like tellurium and iodine

So they were in the same column as other elements with similar chemical properties

Where are metals on the periodic table found?

To the left of the periodic table

Where are non-metals on the periodic table found?

To the right of the periodic table

What is an ion?

A charged atom which has lost or gained electrons (to get a full outer shell)

 What kinds of ions do:

·        metals form?

non-metals form?

·        Metals form positive ions

Non-metals form negative ions

What is the charge on ions formed by:

·        group 1 atoms like Na?

·        group 2 atoms like Mg?

group 3 atoms like Al?

·        Na⁺

·        Mg²⁺

Al³⁺

What is the charge on ions formed by:

·        group 7 atoms like Cl?

group 6 atoms like O?

·        Cl^-

O^2-

What name is given to elements in group 0?

Noble gases

Why are the group 0 elements unreactive?

·        They have a full outer shell of electrons

don’t need to lose or gain electrons

How does the boiling point of group 0 elements change down the group?

Increases down the group

What name is given to elements in group 1?

Alkali metals

List 3 observations when an alkali metal like sodium is placed into a basin of water containing universal indicator

Any 3 from:

·        metal floats

·        fizzing/bubbles

·        metal moves

·        metal dissolves/gets smaller

·        indicator turns blue/purple

What are the products when an alkali metal reacts with:

·        oxygen

·        water

·        halogen?

·        Oxygen > metal oxide

 

·        Water > metal hydroxide + hydrogen

 

·        Halogen > metal halide

Explain why the group 1 elements get more reactive down the group

·        Atoms get bigger so outer electrons further from nucleus

·        weaker attraction from the nucleus to the outer shell

·        easier to lose an electron

What name is given to elements in group 7?

Halogens

Which is the most reactive element in group 7?

Fluorine (at the top)

Explain why the group 7 elements get less reactive down the group

 

(opposite trend to group 1)

·        Atoms get bigger so outer electrons further from nucleus

·        weaker attraction from the nucleus to the outer shell

·        harder to gain an electron

What is a displacement reaction?

Where a more reactive element displaces a less reactive one from a compound