2a Flashcards
What is the mass number of an element?
Number of protons + number of neutrons
What is the atomic number?
Number of protons = number of electrons
What is the relative atomic mass?
It’s mass compared with a carbon-12 atom
What are isotopes?
Atoms of a different element with different numbers of neutrons and different mass numbers
What happens in nuclear fission?
The nucleus of one atom of a large element splits to give two nuclei of smaller elements
What happens in nuclear fusion?
The nuclei of two small atoms join together to form a new element
What happens when metal atoms lose electrons?
Positive ions form
What happens when non-metal atoms gain electrons?
Negative ions form
What are some properties of simple molecular elements and compounds?
- They don’t conduct electricity
- Have low melting and boiling points
- Often gases at room temperature
- Are brittle or waxy when solid
- Have intermolecular forces
- Are insoluble
What are giant covalent structures?
Macromolecules that have very high melting points, are very hard and do not conduct electricity
Why can graphite and metals conduct heat and electricity?
Because of delocalised electrons
What type of force holds the ions together in ionic compounds?
Electrostatic forces acting in all directions
When can ionic compounds conduct electricity?
When they are molten or in solution
Why can’t solid ionic compounds conduct electricity?
Because their particles aren’t free to move
When are covalent bonds formed?
When two atoms share electrons so that they achieve a stable outer shell of electrons
