C3) Atoms, Elements, & Compounds Flashcards
define an element. [1]
made of one type of atom
define a compound [1]
made of more than one type of atom chemically bonded together
define a mixture [1]
2 or more elements/ compounds mixed together that can be separated by physical means
describe properties of metals [7]
- usually solids at room temp.
- malleable
- ductile
- shiny
- high melting & boiling point
- high density
- good thermal & electrical conductivity
what is the difference between a physical change and a chemical change?
physical change = change in state
chemical change = atleast 1 new substance is amde
what is the difference in colour between anhydrous and hydrated forms of copper (II) sulphate?
anhydrous copper sulfate = white
hydrated copper sulphate = blue
what is the difference in colour between anhydrous and hydrated forms of cobalt (II) chloride?
anhydrous cobalt chloride = blue
hydrated cobalt chloride = pink
what is the mass number of an element?
number of nucleons (protons + neutrons)
how are elements arranged in the periodic table?
in ascending atomic number
define an isotope
atoms of the same element with same number of protons and electrons, but diff number of neutrons
why do isotopes have the same chemical properties?
bc they have the same number of electrons in their outer shell
how do metal atoms form ions?
lose electrons to form positive ions
how do non-metal atoms form ions?
gain electrons to form negative ions
describe an ionic bond
the electrostatic attraction between positive metal ions and negative non metal ions
what type of structure do ionic substances form?
giant ionic lattices
describe the properties of ionic substances [4]
- low volatility
- high solubilkity
- high melting/boiling point
- conducts when molten / aqueous
explain the high melting/boiling point of ionic substances.
strong electrostatic forces of attraction between ions that requires a lot of energy to overcome
explain the electrical conductivity of ionic substances
able to conduct when molten/aquous bc ions are free to move and carry charge
describe a covalent bond
shared pair of electrons between non-metal ions
describe the properties of covalent substances [4]
- high volatility
- low solubility
- low melting/boiling point
- does not conduct electricity
explain the low melting/boiling point of covalent substances
weak INTERMOLECULAR forces that require a small amount of energy to overcome
explain why simple covalent structures dont conduct electricity
no free mobile charge carriers to carry charge through the structure
name 3 covalent macromolecules
- diamond
graphite
silicon oxide
describe the structure of diamond [3]
- giant structure
- made of carbon atoms
- each carbon forms 4 bonds with another carbon
describe the structure of graphite [4]
- giant structure
- made of carbon atoms
- each carbon forms 3 bonds with another carbon
- layered structure
describe the structure of silicon oxide [2]
- giant structure
- one silicon atom for every 2 oxygen atoms
explain why diamond, graphite and silicon oxide have a high melting/boiling point [2]
lots of strong covalent bonds that require a lot of energy to overcome
why can graphite conduct electricity? [3]
carbon atoms only form 3 carbon bonds so one valence electron is free and delocalised and can carry charge through the structure
explain why graphite is slippery [2]
- weak intermolecular forces between layers
- can slide off each other
what is graphite used for
lubricant and a conductor
what is diamond used for
cutting tools
