Topic 2: Atoms, elements and compounds Flashcards
What are elements?
Elements are pure substances, containing only one type of atom.
They cannot be separated.
Some exist as single atoms (e.g. helium, neon and argon)
Some exist as molecules (e.g. oxygen)
What are compounds?
Compounds are substances containing different elements chemically combined.
They cannot be separated without a chemical reaction.
E.g. H2O, CO2
What are mixtures?
Mixture are impure substances that contain more than one substance not chemically bonded.
They can be separated without a chemical reaction.
What is an atom?
The smallest piece of an element that can exist.
State the subatomic particles of atoms.
Protons
Neutrons
Electrons.
Where are the protons located?
In the nucleus
Where are the neutrons located?
In the nucleus
Where are the electrons located?
In energy levels around the nucleus.
State the relative mass of a proton.
1
State the relative charge of a proton
+1
State the relative mass of a neutron.
1
State the relative charge of a neutron
0
State the relative mass of an electron.
Negligible/Almost zero
State the relative charge of an electron.
-1
What is the proton number?
The number of protons/electrons
What is the nucleon number?
The number of protons + neutrons.
Also known as mass number
How many electrons can the first energy level/shell hold?
2 electrons.
What does the period number tell you?
The number of electron shells in the atoms.
What does the number of electrons in the outer most shell tell us?
Which group the atom can be found in.
What are isotopes?
Atoms of an element with different numbers of neutrons but the same proton number.
Do isotopes have the same electronic configuration?
Yes. This means that the reactivity also remains the same.
How are isotopes used in medicine?
Tracers - to map a path through different body systems
Sterilising equipment
Diagnosing diseases (e.g. cancer)
Radiotherapy - treating cancer.
How are isotopes used in industry?
Tracers - to find out what is happening inside an object without opening it.
Somke alarms
Dating rocks (carbon dating)
Nuclear power stations
What are the two types of isotopes.
Radioactive
Non-radioactive
What are radioactive isotopes?
An isotope with an unstable nucleus.
Write the formula to find the relative atomic mass of an element.
How are ions formed?
When an atom loses or gains electrons from their outermost electron shell.
What are metal ions?
Cations
What are non-metal ions?
Anions
Describe the structure of an ionic compound.
An ionic compound is a giant structure of ions.
The ions have a regular, repeating arrangement called an ionic lattice.
The lattice is formed because the ions attract each other and forma regular patter with oppositely charged ions next to each other.
How are ionic compounds formed?
When metal atoms react with non-metal atoms.
They lose their outer electrons which the non-metal atoms gain to form positive and negative ions.
The positive and negative ions are held together by strong electrostatic forces of attraction between opposite charges.
This force of attraction is known as an ionic bond, which hold ionic compounds together.
State the physical properties of ionic compounds.
- They are hard to break due to the presence of the strong force of attraction between the positive and negative ions.
- They are considered brittle. They generally break into pieces when pressure is applied.
- They have high melting and boiling points
- They are soluble in polar solvents
- They do not conduct electricity in the solid state but only in the molten state.
When does covalent bonding occur?
When two non-metal atoms share a pair of electrons
State the properties of covalent compounds.
- Low melting and boiling points because the intermolecular forces are much weaker than the strong covalent bonds in molecules.
- Poor conductors of electricity.
State the properties of giant covalent structures.
- Extremely strong as they contain many bonds.
- Arranged into giant regular lattices.
Name the allotropes of carbon
Graphite
Diamond
State the uses of graphite.
stationary
lubricants
industries
nuclear reactors
State the uses of diamonds.
Jewelery making
construction
minor industrial applications
surgeries
cutting tools.
State the properties of graphite.
State the properties of diamond
State the properties of silicon (IV) dioxide.
