Model of the Atom, Relative Atomic Mass, Charge + Isotopes

What is an atom?

An atom is the smallest part of an element that can exist.

What is an element?

An element is a substance made up of only one type of atom.

How are the elements listed?

They are listed in the periodic table.

How many elements are there approximately?

100

Elements can be classified into two groups based on their properties; what are these groups?

Metals and non-metals

Elements may combine through chemical reactions to form new products; what are these new substances called?

Compounds

What is a compound?

Two or more elements chemically bonded in fixed proportions.

Do compounds have the same properties as their constituent elements?

No, they have different properties.

What is a mixture?

A mixture consists of two or more elements or compounds not chemically combined together.

Do mixtures have the same chemical properties as their constituent materials?

They do have the same chemical properties.

What are the methods through which mixtures can be separated?

Filtration, crystallisation, simple distillation, fractional distillation and chromatography.

Do the 5 methods of separating mixtures involve chemical reactions?

They do not involve chemical reactions.

Explain simple distillation.

The liquid boils off and condenses in the condenser. The thermometer will read the boiling point of the pure liquid and we get to keep the liquid.

What is simple distillation used to do?

Simple distillation is used to separate liquid from a solution.

Explain crystallisation/evaporation.

The solution is heated until all the solvent evaporates. Crystallisation involves removing only some solvent to form a saturated solution, then cooling it for the solid to form crystals, which are then collected by filtration.

What is crystallisation/evaporation used to do?

Evaporation is used to separate a solid dissolved in a solvent.

Explain fractional distillation

A fractionating column containing glass beads is placed on top of the flask, allowing repeated condensing and vaporising, separating liquids at different heights.

What is fractional distillation used to do?

Fractional distillation is a technique for separation of a mixture of liquids with different boiling points.

Explain filtration

The solid is caught in the filter paper, while the liquid (filtrate) passes through.

What is filtration used to do?

Filtration is used to separate an insoluble solid (residue) suspended in a liquid.

Explain chromatography

In paper chromatography, the solvent rises up the paper, separating the mixture spot into its individual components.

What is chromatography used to do?

Chromatography is used to separate a mixture of substances dissolved in a solvent.

What is a separating funnel?

A separatory funnel is an apparatus for separating immiscible liquids (liquids that do not mix). The liquid with greater density forms the bottom layer and can be run off.

Describe the plum-pudding model

The atom is a ball of positive charge with negative electrons embedded in it.

Describe the Bohr/nuclear model.

The nuclear model suggests that electrons orbit the nucleus at specific distances (shells).

How did the Bohr/nuclear model come about?

It came about from the alpha scattering experiments.

Later experiments led to the discovery of smaller, positive particles in the nucleus; what are these particles called?

Protons

What did the work of James Chadwick provide evidence for?

The existence of neutrons in the nucleus

Describe the structure of an atom

The atom has a small central nucleus (made up of protons and neutrons) around which there are electrons in shells

What is the relative mass and charge of a proton?

Mass: 1, Charge: +1

What is the relative mass and charge of a neutron?

Mass: 1, Charge: 0

What is the relative mass and charge of an electron?

Mass: very small, Charge: -1

Explain why atoms are electrically neutral.

They have the same number of negatively charged electrons and positively charged protons so the charges cancel out.

What is the radius of an atom?

0.1 nm (1 × 10^-10 m)

What is the radius of a nucleus and what is it compared to that of the atom?

1 × 10^-14 m and about 1/10,000 the size of the atom.

What name is given to the number of protons in the nucleus?

Atomic number

Atoms of the same element have the same number of which particle in the nucleus?

Protons

Where is the majority of mass of an atom?

The nucleus

What is the mass number?

The total number of protons and neutrons

How does one calculate the number of neutrons using mass number and atomic number?

Mass number - Atomic number

What is an isotope?

Atoms of the same element that have a different number of neutrons.

Do isotopes of a certain element have the same chemical properties?

They have the same chemical properties as they have the same electronic structure.

What is the relative atomic mass?

The average mass value which takes the mass and abundance of isotopes of an element into account. on a scale where the mass of ¹²C is 12.

Give the electronic configuration of He (2).

He: 2

Give the electronic configuration of Be (4).

Be: 2,2

Give the electronic configuration of F (9).

F: 2,7

Give the electronic configuration of Na (11).

Na: 2,8,1

Give the electronic configuration of Ca (20).

Ca: 2,8,8,2

What are ions?

Ions are charged particles.

How are ions formed?

They are formed when atoms lose or gain electrons.

When an atom loses electrons, what charge does its ion have?

Positive charge

When an atom gains electrons, what charge does its ion have?

Negative charge

Substance A contains only one type of atom. Substance A does not conduct electricity. Which type of substance is A?

Non-metallic element

Substance B contains two types of atoms. The atoms are chemically combined together in fixed proportions. Which type of substance is B?

Compound