Unit 4 Flashcards
(32 cards)
What is the periodic table
A list of all the elements, in order of increasing atomic number
What are the columns called in the periodic table
Groups
What are the rows in the periodic table called
Periods
What does the group number tell you
How many electrons that are in the outer shell of the atoms
What are Vallency electrons
The outer shell electrons
Group 1
The alkali metals
Group 2
Alkaline earth metals
Group 7
The halogens
Group 0
The noble gases
Periods
The period number gives information about the number of electrons shells that are available in that period
Hydrogen
Hydrogen sits alone in the table because it’s the only element with one electron shell
Trends in the periodic table
The elements in each numbered group show trends in their properties. For example as you go down group 1, the elements become more reactive or as you go down group 7 elements become less reactive and so on
Group 1-alkali metals
Physical properties
Chemical properties
Their physical properties:
- Like all metals, they are good conductors of heat and electricity.
- They are softer than most other metals.
- they have low melting and boiling points, compared to most metals
Their chemical properties:
- All alkali metals react vigourously with water, releasing hydrogen gas and forming hydroxides. The hydroxides give alkaline solutions.
- They react with non-metals. With chlorine they react to make chlorides and with oxygen they make oxides.
They form ionic compounds in which the metal ion has a charge of positive one. The compounds are white solids, which dissolves in water to give a colourless solution.
The trend in physical properties (group 1) As it goes down Softness increases Density increases Melting points decrease Boiling points decreases
Lithium Sodium Potassium Rubidium Season
Why did they have similar properties
Because atoms of the same number of Vallency electrons react in a similar way
Why The further you go down the group reactivity increases
Because the atoms get larger down the group because they add electron shells
Group 7-the halogens
I’m nonmetal group
From coloured gases
Are poisonous
Are brittle and crumbly in their solid form, and do not conduct electricity
Form diatomic molecules (means they exist as 2 atoms)
Trends in their physical properties ( group 7) As you go down : Size and mass of atom increases Density increases Melting and boiling points increase
Chlorine
Bromine
Iodine
Why does the reactivity increase as you go up group 7
Because the smaller the atom, the easier it is to attract the electron - so the more reactive an element will be
Why are they so reactive (group 7)
Because their atoms are only one electron short of a full shell
Group 0: the noble gases
A non-metal group
Contains colourless gasses, which occur naturally in air
Monatomic-they exist as single atoms
Unreactive because they have a full outer shell
Trends in their physical properties (group 0) As you go down Size and mass of atom increases Density of gas increases Boiling points increases
Helium Neon Argon Krypton Xenon
Uses of noble gases
Noble gases are unreactive, making them safe to use. They also grow when current is passed through them at low pressure.
Use of helium (noble gases)
Used to fill balloons and airships, because it is much lighter than air and will not catch fire.
