1.1 Model of the Atom
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What do chemical symbols represent? e.g. Na and O
An atom of an element Na- represents atoms of sodium O- represents atoms of oxygen
How are compounds formed?
From elements by chemical reactions
What do chemical reactions involve?
• Formation of one or more new substances • Often a change in energy
What is a compound? Give an example
Two or more elememts that are chemically combined in fixed proportions HCl NaCl
How are compounds separated back into elements?
Only by chemical reactions
What is a mixture?
Two or more elements or compounds not chemically combined
What is the difference between a compound and a mixture?
Compound - Two or more elements chemically combined - Only separated by a chemical reaction Mixture - Two or more elements or compounds not chemically combined - Can be separated by physical processes
How can a mixture be separated?
Filtration Crystallisation Simple distillation Fractional distillation Chromatography
What is the plum pudding model of the atom?
Atom is a ball of positive charge with electrons in it
What experiment proved the plum pudding model was incorrect?
Alpha particle scattering experiement
What was done in the alpha particle experiment?
• Beam of alpha particles aimed at thin gold foil • Some particles detected at different angles and some came back straight • Alpha particles were being repelled and deflected by positively charged nucleus
What is an alpha particle?
2 protons and 2 neutron nucleus Therefore He2+
Fill in the table
What is the charge of an atom?
0 Number of protons is equal to number of electrons
Fill out the table
What is the mass number?
Sum of protons and neutrons in an atom
What is an isotope?
Atoms of the same element with different numbers of neutrons
What is relative atomic mass?
Average mass of an element or compound that takes account of abundance of isotopes of the element
What energy level do electrons occupy?
Lowest available energy level (or shell) (Shell closest to the nucleus)