1.6 Periodic Table
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Features of Mendeleev’s periodic table and date
Fewer elements as it had gaps for undiscovered elements (enabling him to predict the properties of undiscovered elements (noble gases hadn’t been discovered yet)) Arranged in order of atomic mass No block of transition metals No noble gases No actinides or lanthanides Published 1869
Features of the modern day periodic table
More elements with no gaps Arranged in order of atomic number Block of transition metals Noble gases Actinides and lanthanides
Group
A vertical column in the periodic table
Period
A horizontal row in the periodic table
Elements in the same group…
Have the same number of electrons in their outer shell, meaning they also have similar chemical properties
Groups that have elements of similar chemical properties
Group 1 alkali metals (reactive) Group 2 alkaline Earth metals (reactive) Group 7 halogens (reactive non metals) Group 8 noble gases (unreactive non metals)
Where are metals and non metals on the periodic table
To the left of the black line are metals To the right of the black line are non metals
Properties of metals
Conduct heat and electricity Malleable and ductile High melting point Sonorous
Properties of non metals
Doesn’t conduct heat or electricity Not malleable and ductile Low melting point Not sonorous
Elements which occur as gases at room temperature
Hydrogen, nitrogen, oxygen, fluorine, chlorine, helium, neon, argon, krypton, xenon and radon
Elements which occur as liquids at room temperature
Bromine and Mercury
Group 1 info
Alkali metals Very reactive, more reactive than group 2 Have a low density (first three are less dense than water Li, Na and K so they float) Stored under oil to prevent it reacting with moisture/oxygen in the air Soft and easily cut, exposing a shiny surface, but tarnish rapidly in air Forms an ion with charge of + eg Na —> Na+ + e-
Why do alkali metals have similar chemical properties
When they react an atom loses an electron to form a positive ion with a stable electronic configuration
Group 1 elements as they move further down the group
Low melting points decrease Atoms increase in size Increasingly reactive
Why do group 1 metals get more reactive further down the group
The size of the atom increases down the group, meaning the outer electron to be lost is further away from the attractive positive charge of the nucleus, therefore it can be more readily lost. Additionally there are more electrons between the outer shell and the nucleus, and these inner electrons shield the outer electrons from the attractive power of the nucleus and
Group 1 metals reaction with water
Forms a metal hydroxide (in solution) and hydrogen eg sodium + water = sodium hydroxide + hydrogen These reactions are highly dangerous as these metals are all highly reactive. They are stored under oil to prevent them reacting with moisture and oxygen in the air
Lithium reaction with water
Group 1 metal Metal floats, moves about the surface, fizzes/releases a gas, eventually disappears, heat released, colourless solution forms
Sodium reaction with water
Group 1 metal Metal floats, melts into a silver ball, moves about the surface, fizzes/releases a gas, eventually disappears, heat released, colourless solution forms
Potassium reaction with water
Group 1 metal Metal floats, moves about the surface, burns with a lilac flame, fizzes/releases a gas, eventually disappears, heat released, small explosion/crackle, colourless solution forms
Group 7 info
Reactive non metals Coloured Toxic Exist as diatomic molecules Does not conduct electricity Forms a simple halide ion with a charge of - React with group 1 metals to form solid, white, ionic compounds
Group 7 elements going down the group
Reactivity decreases down the group
Fluorine at room temperature
Group 7 non metal Yellow gas
Chlorine at room temperature
Group 7 non metal Yellow-green gas
Bromine at room temperature
Group 7 non metal Red-brown liquid