Chemistry -Year 9 Term 1.1

Atoms, periodic table, states of matter, separation techniques, diffusion

Parts of an atom

Nucleus and shells

What sub-atomic particles are found in the nucleus of an atom?

Protons and neutrons

What sub-atomic particles are found in the shells of an atom?

electrons

How many of each sub-atomic atoms would you find in a neutral atom?

Electrons = protons Neutrons = ??

charge of a neutron

0

Charge of an electron

-1

charge of proton

+1

Fill the blanks

The atomic model has ______ over time

Why do neutral atoms have the same number of protons as the number of electrons

Because protons have positive charge of +1 while electrons have negative charge of -1. Thus, they cancel each other out, keeping the atom neutral

What does the atomic number state?

The number of protons (which is the same as the number of electrons as long as the atom is neutral)

What does the mass number state?

The number of protons (which is the same as the number of electrons as long as the atom is neutral) and neutrons combined

How do you calculate the number of neutrons in an atom?

Mass number - atomic number

Electron configuration for the first 20 elements

first shell

symbol of electron

e- (- should be higher)

symbol of proton

p

symbol of neutron

n

mass of electron

negligible

mass of proton

1

mass of neutron

1

Which element is the only element that does not belong to any group?

hydrogen

Who constructed the periodic table?

Dimitri Mendeleev

What does the period number represent

number of occupied shells

What does the group number represent?

The number of electrons on the outermost shell

Isotopes

Atoms of an element that have the same number of protons but different number of neutrons

Fill the blank

Period run in _____

Fill the blank

Groups run in ___

Describe properties of isotopes to its element

Same chemical properties but slightly different physical ones.

How many neutrons does the isotope H-3 have? (Hydrogens have one proton)

2

Relative atomic mass

Average mass of an element's atoms compared to 1/12th of the mass of a carbon-12 atom (1 relative mass unit since 12/12 is 1)

Relative mass formula

Combination of (isotope 1's mass x abundance/percentage in decimal) until all types of isotopes have been added

Duplet (in chemistry)

When an atom's first shell contains 2 electrons (the outermost shell is filled with 2 electrons)

Octet (in chemistry)

When an atom's outermost shell contains 8 electrons and thus that shell is filled

Group 0(18)

Noble gases

2 characteristics of noble gases

• all unreactive
• all octet except for helium which is duplet

explain why noble gases are unreactive

because they are all either a octet or duplet, they all have a full outermost shell, giving them stability and making them unreactive because they have lower energy

Why is group 0 not group 8

Because not all elements in group 0 have 8 electrons in their outermost shell. (Helium has 2)

Arrangement of particles in a solid

Closely packed in a lattice

Arrangement of particles in a liquid

closely and randomly packed

Arrangement of particles in a gas

far apart, random arrangement

Movement of particles in a solid

Vibrate about a fixed position

movement of particles in a liquid

Slide past one another (Still touching)

Movement of particles in a gas

Moving rapidly and randomly in all directions

Shape of liquid

takes up the shape of the container

shape of gas

takes up the volume of the container

are liquids compressible

No

Are gases compressible?

yes

why can liquids not be compressed?

There is not enough space between particles in a liquid since they are touching.

State change from solid to gas

sublimation

state change from gas to solid

deposition

What temperature does evaporation occur

any temperature

what temperature does boiling occur

at boiling point

where does evaporation occur

on the surface of the liquid

where does boiling occur

throughout the liquid

Why does Helium not belong in group 2

Because all elements in group 2 are metal, while helium is not.

State change from solid to liquid

melting

State change from liquid to solid

freezing

State change from liquid to gas

evaporation

State change from gas to liquid

condensation

How are elements chosen to be in the same groups?

They have similar properties

What has allowed people to predict elements that weren't discovered yet?

Grouping elements in the periodic table by their similar properties

what does the same number of outer electrons among a group of elements allow?

similar chemical properties

what is the difference between group 0 and the rest of the elements?

elements of group 0 are unreactive, while the other element are reactive

what are the 2 ways elements in group 0 attain stable electron structure?

forming ionic bond or forming a covalent bond

Which of the sub-atomic particles in an atom never change?

Protons

What does 2+ ion mean?

losing 2 electrons

why does 2+ ion mean losing electrons even though it is a plus sign?

Because electrons are negative

What should you write in an exam question that asks for the name of an element?

JUST the name. Eg: "Boron", not "Boron(B)"

Lattice

repeating pattern

Diffusion

Net movement of particles from an area of higher concentration to an area of lower concentration

Why does diffusion happen? (Think of particles' movement)

Because particles are moving randomly (See chemistry book with orange and green highlighted page to understand)

Element

A substance made of one type of atom that cannot be broken down into simpler substances

Compound

Two or more types of atoms that are chemically bonded together

Pure substance

only one type of substance (could be element or compound)

Mixture

Two or more substances mixed together but not chemically bonded

Molecule

group of atoms bonded coefficiently together, like water

What happens to the boiling point when something is impure?

the boiling point decreases

Supercritical fluid properties(not needed for iGCSE)

Has properties of gas and liquid

Name all the separation techniques

Decantation, Filtration, Distillation, Evaporation, Crystallisation, Chromatography

Which separation methods separate insoluble solids from a solution?

Decantation and Filtration

Solvent

the dissolving medium in a solution

Solute

A substance that is dissolved in a solution.

Which separation methods separate soluble solute and a solvent from a solution?

Distillation, evaporation, crystallisation

Crystal

a pure substance in solid state and in a lattice