Chemistry
Periodic Table
the top number on the element is the mass number- number of protons+neutrons
Atomic Structure
same amount of electrons and protons
neutrons and protons found in the nucleus
electrons are found in the shells around the atom
the shell closest to the nucleus can contain 2 electrons and then all the other shells can contain 8 electrons
each element contains a different amount of electrons, neutrons and protons
number of neutrons= mass number-protons
the atomic number is on the bottom- number of protons and electrons
there are 118 elements
horizontal rows are called periods
vertical columns are called groups
metals are on the left side of the periodic table and non-metals are on the right
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Solutions- one or more solutes dissolved in a solvent.
Solvent- a solvent is a liquid in which solutes are dissolved.
Solute- the substance that is dissolved in the solvent.
Insoluble solutes- don't dissolve in the solvent.
Soluble solutes- can dissolve in solvents.
Key processes
Evaporation- when water is heated to turn it into a vapour.
Crystallization- evaporating the solution to get rid of the solvent and be left with the soluble solute in the form of crystals.
Filtration- separating the solvent from the insoluble solute.
Simple distillation- separating mixtures based on differences of volatilities and boiling points.
Fractional distillation- separating mixtures of similar boiling points by boiling them at a temperature that will vaporize some of the mixtures. The mixtures are separated and put in order) in a big container based on their boiling points.
Compound
A mixture is two or more elements and compounds that are not chemically bonded.
An element is only made of one type of atom.
A compound is two or more elements that are chemically bonded.
Isotopes
Isotopes are two or more types of atoms that have the same atomic number and position in the periodic table.
An isotope is one of two or more species of atoms of a chemical element with the same atomic number and position in the periodic table and nearly identical chemical behavior but with different atomic masses and physical properties.
Every chemical element has one or more isotopes.
Discovery of the atom
John Dalton: 1766-1844. Suggested that atoms are solid spheres and that different spheres make up different elements.
JJ Thompson: 1897. Used the 'plum pudding model' to show that atoms must be a general ball of positive charge (the pudding) and must contain contain negatively charged particles- electrons (the plums).
Ernest Rutherford: 1909. Fired positively charged alpha particles at a thin sheet of gold to prove JJ Thompson's theory that particles are spread out. He proposed that if the gold particles were as spread out as Thompson said, then the alpha particles should pass right through as there wouldn't be any concentrated positive charge to repel them. However, they didn't so he proposed that the positively charged particles were stored in a nucleus, and the negatively charged particles exits in a cloud around the nucleus (nuclear model).
Niels Bohr: 1913. Suggested that electros orbit the nucleus in shells which stop the atom from collapsing.
James Chadwick: Discovered that neutrons as well as protons are stored in the nucleus of the atom.