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BTEC 2012 UNIT 2 (CHEMISTRY) ASSIGNMENT 1 GROUPS 1 & 7 OF THE PERIODIC TABLE
Transcript of BTEC 2012 UNIT 2 (CHEMISTRY) ASSIGNMENT 1 GROUPS 1 & 7 OF THE PERIODIC TABLE
GROUPS 1 & 7
GROUP 1 ELEMENTS
The elements in groups 1 & 7 are very reactive.
Moving down group 1 reactivity increases, but decreases moving down group 7
This is due to the electron structure (and the size of the atoms) of the elements
All elements 'want' to achieve a full outer shell
Group 1 elements have 1 electron in their outer shell so they lose 1 electron when they react
Group 7 elements have 7 electrons in their outer shell so they gain 1 electron when they react
Moving down both groups the atoms get bigger BUT reactivity increases in group 1 & decreases in group 7
The more easily electrons are lost or gained the more reactive the element
the smaller an atom is the better it is at gaining electrons. If the atom is smaller, the positive nucleus is closer to the outer electron shell and the better it is at attracting electrons.
the bigger an atom is the better it is at losing electrons. If the outer electron shell is further from the nucleus, the electrons are less attracted to the nucleus and are more easily lost
GROUP 7 ELEMENTS
REACTIVITY & ELECTRON STRUCTURE
Group 1 elements are:
shiny (when freshly cut)
they react readily with air & water (this means they have to be stored in oil) e.g.
sodium + oxygen --> sodium oxide
lithium + water --> lithium hydroxide + hydrogen
Group 7 elements are:
They have low melting & boiling points
Fluorine & Chlorine are gases, Bromine is a liquid & Iodine is a solid
They are toxic ( especially F, Cl & Br)
They react with each other in displacement reactions
Chlorine + potassium Bromide --> bromine + potassium chloride
The physical properties of the elements in groups 1 & 7 change as you move down the group
Melting point & boiling points change in both groups
Density increases in both groups
Colours change in group 7