Atoms, elements and compounds Flashcards
Differences between elements,compounds and mixtures
- Elements contain only one type of atom
- A compound is a substance containing 2 or more different types of atoms bonded together.
- Mixture contains 2 or more elements or compounds that are not chemically bonded together.
What are protons and neutrons called?
Nucleons
Which 2 subatomic particles have the same mass?
Proton and neutron
Define isotope
Atoms which have the same proton number, but different nucleon number.
How are ions formed?
When atoms lose or gain one or more electrons.
Describe the formation of ionic bonds between metals and non-metals
- Metals from positive ions by losing electrons
- Non metals form negative ions by gaining electrons except hydrogen
What is covalent bonding?
When two non-metal atoms react , they share a pair of electrons.
Describe the solubility, volatility and conductivity in ionic compounds
- High mp/bp(strong attractive forces)
- Soluble in water (water molecules are able to separate the ions from one another
- Conduct electricity only when molten or dissolved in water, because the ions are mobile
Describe the solubility, volatility and conductivity in covalent compounds
- Low mp/bp except silicon dioxide
- Insoluble in water except sugars and amino acids
- Do not conduct electricity because they have no ions.
Define relative molecular masses
The sum of the relative atomic masses
Define electrolysis
The chemical effect of electricity on ionic compounds,causing them to break up into simpler substances
What is usually formed at cathode?
Metals- if it less reactive than hydrogen
Hydrogen-if it is less reactive than metal
What is usually formed at anode?
Halides if its is in group 7 or oxygen
Define allotropes
Different forms of the same element
Why diamond are so hard?
The carbon atoms link together to form giant lattice
