Elements and compounds
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Element
a pure substance made up of only one type of atom (eg. gold atoms make up the element of gold or AU)
A chemist heats up some pure ammonia to very high temperature and finds that it breaks down into two other gases. Explain whether ammonia is an element or not.
Ammonia is not an element as it is made up of two different atom types which separated in the form of gases.
Noble gases
elements that are found in singular atomic form
molecules
single atoms bonded together chemically
Most elements have a structure of
lattices
Lattices
Multiple atoms that are chemically bonded together in continuous framework
Which state of matter do lattices form?
Solids due to the crystal structure
Which state of matter do molecules form
liquid and gases and solids
which state of matter do single atoms form?
gases
properties
a determination of how an element reacts or behaves
properties of metal
• conducts heat • conducts electricity • ## shiny appearance
When writing a chemical formula, what are the rules for the order of the elements?
If the elements are in the same column, the element on the bottom goes first. The element on the left of the periodic table row is written first.
Where are most of the non-metal elements held in the periodic table?
In the upper right corner
In the periodic table, barium sits directly underneath strontium. Propose two things that you can say about barium and strontium with just this information.
Barium has similar properties to Strontium and Strontium has less atomic weight than Barium.
Compounds
substance that has atoms of two or more elements (atom types) joined together through chemical bonds
mixture
combination of substances that are not chemically bonded so they can actually be separated physically.
Water is a compound of Hydrogen (H) and Oxygen (O). Its chemical formula is H2O. Determine the number and type of atoms in each molecule of WATER.
Water has two hydrogen atoms and one oxygen atom.
Sulfur dioxide is a gas released by volcanoes. Each molecule contains one sulfur (S) atom and two oxygen (O) atoms. Identify its chemical formula.
SO2
Determine the general structure of a word equation.
Reactants -> Products
Periodic
Occurring at intervals/ recurring
Summarise the difference between exothermic and endothermic reactions.
Exothermic reactions overall release energy (heat) so the temperature of the surroundings increases. Endothermic reactions overall absorb energy (heat) so the temperature of the surroundings decreases.
Breaking bonds
A process that requires energy from surroundings
Making bonds
A process that releases energy back into the surroundings
Do both endo- and exothermic reactions require energy and release energy?
YES The two steps – the first requiring energy and the second releasing it – take place in all reactions, exothermic and endothermic. The difference is whether the amount of energy released when the new bonds form is greater or less than the energy required to break the old bonds.