C4 - Atoms, Electrons And Ions Flashcards
Why are atoms electrically neutral?
It contains equal numbers of protons and neutrons
What is the atomic number and the mass number?
Atomic number - number of protons it contains ( bottom number)
Mass number - number of protons and neutrons
Define an isotope
Varieties of an element that have the same atomic number but different mass numbers
What is an ion?
An electrically charged atom or groups of atoms
How do ionic bonds form?
When a metal reacts with a non-metal, electrons are transferred from the metal atoms to the non-metal atoms. The positive metal ions and the negative non - metal ions attract one another, forming ionic bonds.
What are the similarities and differences between the ionic compounds : magnesium oxide and sodium chloride.
Similarities :
- high melting point
- do not conduct electricity when solid
- conduct when molten
Differences
- sodium chloride can dissolve in water and conduct electricity in solution too
What is a giant ionic lattice?
The ions in the ionic compound are arranged in a regular way. The structure is repeated many times ( not big ). The positive ions are strongly attracted to the negative ions, forming ionic bonds.
Why do ionic compounds have high melting points and an inability to conduct when solid ?
High melting point : ionic bonds = strong chemical bond. A lot of energy is needed to break them.
Inability to conduct when solid : to conduct, ions must be free to move from place to place. This can happen when molten or in solution , but not in a solid.
How can you work out what group and period an object is in from its electronic structure?
- the period is the number of numbers
- the group is the last number
E.g silicon = 2.8.4
Period = 3rd
Group = 4
What are covalent compounds and covalent bonds?
Covalent compound = non - metals combined with each other
Covalent bond = a shared pair of electrons
Explain why simple compounds like carbon dioxide and water have low melting points and can’t conduct electricity.
Simple molecule = each molecule contains a few atoms joined by covalent bonds. Although these bonds are strong , the intermolecular forces between the molecules are weak. Little energy is needed to overcome them so low boiling point.
Carbon dioxide and water have no overall electronic charge. Their electrons are not free to move from place to place , so these compounds do no conduct electricity.
What do you use the two different dot and cross diagrams to show?
2 dot and cross diagrams showing all shells and electrons. Showing where electron gained/lost with arrows. Bracket around ion diagram with + or - in corner. = ionic bonding between metal and non - metal. Metal = dot , non-metal = x
Single dot and cross diagram with only outer shell with electrons shown. Shows shells linked together and sharing electrons to complete them = covalent bonding between non - metals. Bonded atom = dot, other atom = cross
