C2 Keywords Flashcards
define atom
The smallest part of an element that can exist.
define electron
Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons.
Define plum pudding model
The scientific idea that an atom is a sphere of positive charge, with negatively charged electrons in it.
Define alpha particle
Subatomic particle comprising two protons and two neutrons (the same as a helium nucleus)
Define vacuum
A volume that contains no matter.
Define nucleus
The central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. The plural of nucleus is nuclei.
define proton
Subatomic particle with a positive charge and a relative mass of 1. The relative charge of a proton is +1
define neutron
Uncharged subatomic particle, with a mass of 1 relative to a proton. The relative charge of a neutron is 0.
define mass
The amount of matter an object contains. Mass is measured in kilograms (kg) or grams (g).
define element
A substance made of one type of atom only.
define atomic number
The number of protons in the nucleus of an atom. Also called the proton number.
define mass number
The number of protons and neutrons found in the nucleus of an atom.
define ionise
To ionise is to convert an uncharged atom or molecule into a charged particle by adding or removing electrons.
define energy levels
Specific amounts of energy that electrons have when they orbit a nucleus is a particular shell. Electrons that gain energy may move to a higher energy level (a shell further from the nucleus). Electrons that lose energy may move to a lower energy level (a shell closer to the nucleus).
define ion
Electrically charged particle, formed when an atom or molecule gains or loses electrons.
define relative atomic mass
This is the mass of the atom compared with that of the carbon-12 isotope, which has a mass of exactly 12.
define periodic table
A tabular representation of all known elements in order based on atomic number
define noble gases
The elements in Group 0 of the Periodic Table, named for their lack of chemical reactivity.
define group
A vertical column in the periodic table containing elements with similar chemical properties.
define period
A period is a horizontal row in the periodic table.
define metal
Shiny element that is a good conductor of electricity and heat, and which forms basic oxides.
define non-metals
Non element that is a poor conductor of electricity and heat, and which forms acidic oxides.
define Group 1
The first vertical column of elements in the periodic table, starting with lithium and ending with francium. Also called the alkali metals.
define melting point
The temperature at which a solid changes into a liquid as it is heated.
define electronic configuration
The order electrons are arranged in different shells.
define Group 7
The vertical column of non-metal elements next to group 0 in the periodic table, also called the halogens.
define transition metals
A metal that is located in between Group 2 and Group 3 and has brightly coloured compounds.
define Group 0
The vertical column of non-metal elements on the far right of the periodic table, also called the noble gases.
define halogens
An element placed in Group 7 of the periodic table, which starts with fluorine and ends with astatine. The name ‘halogen’ means ‘salt-producing’ because halogens produce a range of salts when they react with metals.
define displacement reaction
Is a reaction in which a more reactive metal takes the place of a less reactive metal in a compound.
define properties
The characteristics of something. In chemistry, chemical properties include the reactions a substance can take part in. Physical properties include colour and boiling point.
define density
A measure of compactness and the ratio of mass to volume. It is usually measured in kilograms per metre cubed (kg/m3) or grams per centimetre cubed (g/cm3)
define alkali
A base which is soluble in water.
define properties
The characteristics of something. In chemistry, chemical properties include the reactions a substance can take part in. Physical properties include colour and boiling point.
define base
A substance that reacts with an acid to neutralise it and produce a salt.
define dissolve
When a substance breaks up and mixes completely with a solvent to produce a solution.
define alkaline
Having a pH greater than 7.
define solution
Mixture formed by a solute and a solvent.
define pH
Scale of acidity or alkalinity. A pH (power of hydrogen) value below 7 is acidic, a pH value above 7 is alkaline.
define reactivity
A measure of how vigorously a substance will react. The more reactive it is, the greater its reactivity and the more vigorous its reactions will be.
define cation
An atom or group of atoms that have lost electrons and become positively charged. Most cations are formed from metals.
define reactive
The tendency of a substance to undergo a chemical reaction.
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define molecule
A collection of two or more atoms held together by chemical bonds.
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