Elements , Compounds And Atoms Flashcards
What is an element?
A substance made up of only one type of atom that cannot be broken down into anything simpler
What is a compound?
A substance containing two or more elements that are chemically bonded together in a fixed ratio
What is a mixture?
A substance containing two or more elements or compounds (in a variable ratio) not chemically combined
What is a molecule?
two or more atoms chemically joined together
why does sodium chloride not fizz when added to water?
- its a compound
- it has different properties to sodium
- it is a completely different substance
What is an electron ?
A subatomic particle found in shells around the nucleus
What are the characteristics of an electron?
-negatively charged
-mass of virtually 0
-found in shells
-can be lost or gained in reactions
What is an atom?
The smallest part of a substance that cannot be broken down chemically
What is an ion?
An atom or a group of atoms that has a net electric charge due to losing or gaining electrons
List the different properties of metal
-shiny
-high melting/boiling points
-malleable
-ductile
-good electrical conductors
-good thermal conductors
What is the relative mass and relative charge of a proton?
Relative mass = 1
Relative charge = +1
What is the relative mass and relative charge of a neutron?
Relative mass = 1
Relative charge = 0
What is the relative mass and relative charge of an electron?
Relative mass = approx 0 (1/1840)
Relative charge = -1
What is the atomic number?
The number of protons and (if neutral) electrons in an atom
What is the mass number?
The sum of the protons and neutrons
what particle is used to determine what element a substance is?
proton
What did James Chadwick discover?
Neutrons (NOT protons)
Describe the plum pudding model
The plum pudding model is the idea that an atom is a sphere of positive charge with negatively charged electrons scattered through it (using a cathode ray tube)
What did Niels Bohr discover?
Electron shells (energy levels)
What did Ernest Rutherford discover?
The nuclear model - atoms have a tiny positive nucleus with negatively charged electrons scattered outside it taking up most of its volume (using alpha particles)
What are isotopes?
Isotopes are atoms of the same element which have the same number of protons but a different number of neutrons
What is the relative atomic mass?
The average mass of an atom (compared to 1/12th the mass of a carbon atom)
How do work out the relative atomic mass?
By multiplying the mass number of the isotopes with its abundance (in percentage) and dividing it by 100
gallium(Ga) is in Group 3 of the periodic table - what is the formula of a gallium ion?
Ga3+
would would oxygen be an unsuitable gas to use in a light bulb?
because its too reactive and would react with the metal
What is the electron arrangement in the energy levels (shells)
2,8,8
What is the group number equal to?
The numbers of electrons in the outer shell
(column)
What is the period number equal to?
The number of shells
(row)
what is the connection between metals , non-metals and electron configuration?
-metals have less than 4 electrons in their outer shell
-non-metals have 4 or more electrons in their outer shell
Which group in the periodic table contains the most reactive metals and why?
Group 1 (the alkali metals)
They only have to lose one electron to gain a full outer shell
why do elements get more reactive as you go down the periodic table
- the outer electron goes further from the nucleus
- the atoms get larger
- the attraction between the nucleus and the outer electron gets weaker
- so the electron is more easily lost
What group in the periodic table contains the most reactive non - metals?
Group 7
They only have to gain one electron to gain a full outer shell
What are elements in group 7 called?
Halogens
What are elements in group 0 called and how does their reactivity change?
Noble gases
They only have to gain one electron to gain an outer shell
what are the elements found in the central block of the periodic table between group 2 and group 3 called?
transition metals
what is the test for hydrogen?
squeaky pop test
why can hydrogen be placed in either Group 1 or Group 7?
because it only has 1 electron meaning it could lose 1 to go in Group 1 or gain 1 to go in Group 7
what is an exothermic reaction?
a chemical reaction in which energy is released to the surroundings making it warmer
what is a positive ion and how is it formed?
a charged particle formed when an atom loses electrons to become positively charged (a cation)
what is a negative ion and how is it formed?
a charged particle formed when an atom gains electrons to become negatively charged (an anion)
