SC17 Groups in the Periodic Table
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How are elements arranged on the periodic table?
• arranged in increasing atomic number • groups all have the same amount of electrons on the outermost shell • periods have the same amount of electron shells
What is group 1 called?
Alkali metals
Why are alkali metals named alkali metals?
They form alkaline solutions when they react with water
What are the physical properties of alkali metals?
• soft metals that can easily be cut with a knife • relatively low densities and low melting points • very reactive
Write a word equation for the reaction of alkali metals with water
group 1 metal + water –> metal hydroxide + hydrogen
Why are alkali metals reactive?
They only have one electron in the outermost shells, which can be lost easily
Describe the reactivity of alkali metals
Reactivity increases as we go down the group
Why does reactivity increase as we go down the group of alkali metals?
The atoms themselves get bigger, so it is easier to lose an electron because there are weaker forces of attraction between the outermost electron and the nucleus
Describe the reaction of lithium with water
Fizzes steadily, slowly becomes smaller until it disappears
Describe the reaction when sodium is added to water
Melts to form a ball, fizzes rapidly, quickly becomes smaller until it disappears
Describe the reaction between potassium and water
Quickly melts to form a ball, burns violently with a lilac flame, disappears rapidly, often with a small explosion
What is the name of group 7?
Halogens
Describe the appearance of chlorine at room temperature
Pale yellow-green gas
Describe the appearance of bromine at room temperature
red-brown liquid
Describe the appearance of iodine at room temperature
Purple-black solid
Describe the physical properties of halogens
• melting and boiling points increase as you go down the group • diatomic molecules • poor conductors of heat and electricity • toxic and corrosive
Why do melting and boiling points increase as you go down group 7?
The intermolecular forces increase as you go down the group, because the atoms get larger, so much more energy is required to get over these forces
What is the test for chlorine gas?
It turns damp blue litmus paper white
Describe the reactivity of halogens
Decreases as you go down the group
Explain the reactivity of halogens
Decreases as you go down the group because its outer shell is further away from the nucleus, which means the electron is harder to take on due to weak intermolecular forces
What does the halogen reaction with metals produce?
Metal halides
What does the halogen reaction with hydrogen produce?
Hydrogen halides
Describe the chemical properties of hydrogen halides
Becomes less stable as you go down the group
When does a halogen displacement reaction occur?
When a more reactive halogen replaces a less reactive halogen