Chemistry IGCSE Unit 2 (Atoms, Elements and Compunds)
what is different about Group 1 metals from the other metals?
Group 1 metals have low melting and boiling points
how are atoms arranged in the Periodic table?
atoms are arranged in the Periodic table in order of their proton number
define isotopes
atoms with the same number of protons but different number of neutrons
define malleable
can be hammered into shapes without breaking easily
define ductile
can be pulled out / drawn into wires without breaking easily
properties of isotopes
chemical properties are the same, physical properties are not the same
define valence electrons
electrons in the outer most shell
what does every atom of the same element have?
every atom of the same element have the same number of protons
which groups are metals in?
group 1, 2 and 3
which groups are non-metals in?
group 4, 5, 6, 7 and 8/0
define lustrous
has a shiny surface when polished
how many electrons do non-metals have in their outer shell?
have 4 or more valence electrons
how many electrons do metals have in their outer shell?
have less than 4 valence electrons
define mixtures
it contains 2 or more elements/compounds that are not chemically bonded together
the number of electrons in the outershell (GROUP NUMBER) determines...
its chemical properties
What are chemical bonds?
links joining the atoms
define sonorous
makes a ringing sound when hit with a hard object
mercury
metal with low boiling and melting point
define alloys
mixtures of metals with other metals / non-metals
what is inside an atom?
mostly empty space + a nucleus
what is the overall charge of an atom
neutral (because protons = electrons)
how to find the neutron number
nucleon number - proton number
what are protons and neutrons also called?
nucleons
how do you find the nucleon number / mass number?
number of protons + number of neutrons
what is the proton number / atomic number?
number of protons in a nucleus of an atom
charge of proton
+ (positive)
charge of electron
- (negative)
physical properties of metals
- dense (high density) - high melting and boiling points - conductors of heat and electricity - shiny (lustrous) - malleable - ductile - sonorous - some are magnetic - solid at room temperature - can be made into alloys
what are noble gases?
- group 8/0 elements - they have full outer shell of electrons - they are stable
chemical properties of metals
- many metal oxides are basic - many metals react with acids to give off hydrogen gas - when they react, metals form positive ions by losing electrons
chemical properties of non-metals
- many non-metal oxides are acidic - most non-metals do not react with acids - when they react with metals, non-metals form negative ions by gaining electrons (except hydrogen, they can form positive ions)
graphite
- only non-metal that conducts electricity and heat - an allotrope of carbon - has a shiny surface
if an atom is stable, what does it mean?
- the atom can not gain / lose electrons easily - it is very unreactive - does not combine with other elements to form compounds
compounds
-always have a fixed amount of each element -elements in compounds can't be separated by physical means (can separate them by chemical means) -have different properties from the elements they were made from
medical uses of isotopes
-cancer treatment -treatment of overactive thyroid glands -locating tumors in the body -sterilize medical equipment
industrial uses of isotopes
-check for leaks in oil and gas pipelines
facts about mixtures
-does not have a fixed amount of each element/compound in it -still have characteristic properties -can be separated by physical methods
radioisotopes
-emits radiation as they decay -nucleus is unstable
elements
-has a unique chemical symbol -have particular properties(distinguish them from other elements) -generally combine to form molecules or giant structures of atoms -rarely exist on their own
other uses of isotopes
-military purposes -date ancient remains -useful in home and workplace(eg. americium-241: smoke detectors)
charge of neutron
0 (neutral, no charge)
relative mass of electron
0.00054 (negligible)
relative mass of neutron
1
relative mass of proton
1
physical properties of non-metals
opposite of metals - low density - low melting and boiling points - does not conduct heat or electricity (insulators) - dull surface (not shiny) - makes dull sound (not sonorous) - not magnetic - usually gas at room temperature - can be added into alloys
what is inside the nucleus of an atom?
protons and neutrons
what are atoms made up of?
protons, neutrons, electrons
define compounds
pure substances made up of 2 or more different types of atom joined together by chemical bonds
two types of isotopes
radioactive(radioisotope) and non-radioactive
what do isotopes differ in?
relative atomic mass
define inert
stable and unreactive (noble)
What are protons, neutrons, and electrons called?
subatomic particles
define elements
substances that are made up of only one type of atom and cannot be broken down into anything simpler by chemical reactions
define electronic configuration / electronic structure
the arrangement of electrons in shells
what does it mean when a atom has a full outermost shell?
the atom is stable
when atoms of other elements combine, what do the compounds formed have?
the compounds formed have the noble gas structure and has full electron shells around each atom
what does the period number in the periodic table tell?
the number of shells an atom of an element has
define atom
the smallest particle that makes up matter and is indivisible
what does the group number in the periodic table tell?
the valence electron(s) of an atom of an element
how many electrons are there in the first outer shell?
there are 2 electrons in the first outer shell
how many electrons are there in the second outer shell?
there are 8 electrons in the second outer shell
what do elements in the same group in the Periodic table have?
they have the same number of outermost shell electrons (valence electrons)
isotopes have the same chemical properties because...
they have the same number of valence electrons
