Atoms,elements and compounds Updated Flashcards
what are all substance made from?
atoms
What is the smallest part of an element that can exist?
atoms
What is an element?
a substance that contains only one type of atom.
How many different elements are there?
about one hundred
What is and is not displayed in the periodic table?
What is shown: element
What is not shown: mixtures, compounds etc.
what are most substances?
compounds
what is a compound
A compound is a substance which is formed by two or more DIFFERENT types of elements which are united chemically in a fixed proportion
what is a chemical formula?
a combination of chemical symbols and numbers
What are chemical formulae used to show?
- the different chemicals in a compound
- how many atoms of each element one molecule of the compound contains
what is the only way that compounds can be separated into their elements?
chemical reactions or electrolysis
what are mixtures?
two or more elements or compounds which are not chemically combined
What do the components of the mixture retain?
e.g. in a mixture of iron and sulfur, the iron is still magnetic and the sulfur is still yellow
mixtures can be separated by _________?
physical processes, these are not chemical processes so no new substances are made
what is filtration used to do?
used to separate soluble solids from insoluble solids e.g. a mixture of salt (soluble) sand (insoluble) by dissolving the salt in water and then filtering the mixture
What is crystallisation used to obtain?
soluble solids from a solution, e.g. salt crystals can be obtained from a solution of salty water
step 1.the mixture is gently warmed
step 2.the water evaporates leaving crystals of pure salt.
What is simple distillation obtaining?
a solvent from a solution
what is chromatography used to do?
it is used to separate the different soluble, coloured components of a mixture, e.g. the different colours added to a fizzy drink can be separated by chromatography
what were atoms though to be in early models?
tiny spheres that could not be divided into simpler particles
What is the overall charge of the atom?
it is neutral
What did Thomson think atoms were?
a sea of positive charge with tiny negative electrons, this is known as the plum pudding model
what is the typical atomic radius?
what is the type about 0.1nm or 1x 10^-10
Why do atoms not have an overall charge?
because they contain an equal number of protons and electrons
what do all atoms of a particular element contain?
the same number of protons
what is the number of protons in an atom actually called?
the atomic number
what the sum of neutrons and protons?
the mass number
How is the periodic table arranged?
in order of atomic number
whats the chemical symbol for Helium?
helium, He
What’s the chemical symbol for Boron?
boron, B
What’s the chemical symbol for beryllium?
beryllium, Be
What’s the chemical symbol for lithium?
lithium, Li
What’s the chemical symbol for Carbon?
carbon, C
What’s the chemical symbol for neon?
neon, Ne
What’s the chemical symbol for sodium?
sodium, Na
What’s the chemical symbol for magnesium?
magnesium, Mg
what is a molecule?
A molecule is a group of two or more atoms held together by chemical bonds.
what is the difference between a molecule and a compound?
a molecule has two or more of the same atoms whilst a compound has two or more different atoms
which non metls naturally exist as molecules?
iodine, I2 bromine, Br2 chlorine, Cl2 fluorine, F2 oxygen, O2 nitrogen, N2 hydrogen, H2
what pneumonic can be used to remember what elements are naturally molecules?
IBring Clay For Our New House.
