Chemistry Flashcards
Element
A substance in its purest form. All the atoms are the same
Molecules
Two or more atoms joined together. There atoms may be the same or different
Compound
two or more different atoms joined together a set of ratio
Atom
Smallest particle of matter with a set composition
Ion
An atom that has lost or gained an electron and has an overall charge
Isotope
A variation of an element. These have the same number of protons but can have a different number of neutrons
A physical Change
is a reversible and involves a change in state. For example: Solid --> Liquid (ice -> water) Solid --> Gas (dry ice -> CO2 gas) The molecular structure does not change
A Chemical Change
Is accompanied by one or more of the following:
colour change
fizzing/gas given off
odor given off
temperature
A new compound is formed with different characteristics and appearance to the reactions. This is irreversible. For example: Sodium in Water
Alkali Metals
Group one of the periodic table. They react with water to form alkaline solutions. They form +1 ions and are very reactive. They must be stored under oil. The are low in density, conduct electricity, are malleable and are shiny.
Alkaline Earth Metals
Group two of the periodic table. They are extracted from oxides on the Earth’s crust. They are less reactive that group one. They form +2 ions, conduct electricity, are malleable and shiny.
Halogens
Group seven of the periodic table and are very reactive. They don’t occur free in nature but as diatomic molecules. They combine with metals to form ionic salts. The states at room temperature change from gaseous to solid as you go down the group.
Noble Gases
Group eight of the periodic table. These are very stable and unreactive as they have eight electrons in their valence shell. They are the rare gases in the atmosphere.
Number of electrons in each energy level (shell)
Shell 1: 2 electrons Shell 2: 8 electrons Shell 3: 8 electrons Shell 4: 18 electrons Shell 5: 32 electrons Shell 6: 50 electrons
Each new _______ has a new electron shell
Period
Each new ______ has the same number of electrons in its outer shell. This is called the valence shell or valence electrons.
Group
