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- author "me"
- tags "Chemistry"
- description ""
- fileName "Chemistry 3: the periodic table"
- freezingBlueDBID -1.0
- Who put elements in order of atomic weight?
- John Newlands and Dimitri Mendeleev
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Why was Newlands' Law Of Octaves criticised?
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It was related to music
- Some elements shared the same gap
- Not all atomic masses were known
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Dobereiner introduced the idea of...
Triads, elements were in groups of three, which worked when not many elements were known.
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Who found a repeating pattern?
John Newlands
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Why was Mendeleevs table better?
It lefts gaps to allow for discovery of elements unknown at the time.
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By leaving gaps Mendeleev was able to...
Predict the properties of unknown elements.
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When were protons, neutrons and electrons discovered?
In the early 20th century
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After the discovery of protons, neutrons and electrons, how was the modern periodic table arranged?
In terms of electronic structure
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The periods are..
The horizontal columns
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What patterns is in the periods?
There is one more shell (energy level) per period.
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What makes the properties of an element characteristic of its group?
They all have the same number of electrons on their outer shell (energy level)
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How many groups are there?
8
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What is the block in the middle called?
The Transition Elements or the Transition Metals
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Group 1 is also known as ...
The Alkali Metals
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Groups 7 is also known as...
The Halogens
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Most of the Alkali Metals are less dense than?
Water, so they float. ALL ALKALI METALS HAVE A LOW DENSITY.
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When an Alkali metal reacts with water, what does it form?
Hydrogen gas and a metal hydroxide (which is alkaline)
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Alkali metals have a ......... melting/boiling point.
Low -it decreases down the period
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Alkali metals have a ............ density
Low
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Alkali metals become ......... reactive down the group.
More
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Why do Alkali Metals have similar properties?
They all have one electron on their outer energy level.
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How does an Alkali Metal react with water?
It fizzes around the surface of the water VIGOROUSLY and then catches fire. The more reactive ones catch fire immediately and some explode.
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Why do Alkali Metals become increasingly reactive down the group?
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The outer energy level is further away from the nucleus
- There is less attraction between the nucleus + and the electron - (+ and - = attract)
- There are more electrons between the electron and nucleus which repel (- and - = repel)
- This forces the electron away from the nucleus and so it is lost more easily
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What is reactivity?
When an element/compond loses or gains an electron.
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If a metal hydroxide is dissolved in water, what happens?
An alkaline solution is produced
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How can you test for an alkaline solution?
Use universal indicator (which will turn purple/blue)
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When alkali metals react with non-metals, what type of compound is formed?
Ionic compound
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What happens when an ionic compound is formed?
The metal ATOM loses and electron and becomes a metal ION with a positive charge (+1)
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What colour are ionic compounds and what colour solution is formed?
WHITE compounds which dissolve in water to form COLOURLESS solution.
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The halogens are..
Non-metals
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How many elements in group 7?
5
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The halogens have an ............ melting/boiling point
Increasing. (down the group)
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Halogens vapours are what colour?
Colourless, but some smell particularly strong
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Halogens exist as molecules made up of how many atoms?
2 atoms (pairs)
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Why is it called the periodic table?
Similar properties occur at regular intervals
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Halogens become ........ reactive down the group
LESS
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Why do halogens all have similar properties?
They all have 7 electrons in their outer shell
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Why does the number of electrons in the outer shell effect the reactivity of the halogens?
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The electronic shell gets further away from the nucleus
- There is less attraction to the nucleus
- It is harder to attract an electron
- Reactivity decreases down the group
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When halogens react with metals, they form...
Ionic salts
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What is a halide ion?
A chloride, bromide or iodide ion
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A halide ion carries what charge?
Negative (-1)
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When a halogen reacts with another non-metallic element, it forms what type of compound?
A molecular compound
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In an aqueous solution of its salt, how is a halogen displaced?
A more reactive halogen will displace a less reactive halogen from an aqueous solution of its salt.
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What is the block between group 2 and 3 called?
Transition metals
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Where in the periodic table are the transition metals?
Between groups 2 and 3
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Transition metals form
Coloured compounds
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Transition metals have ions with different ........
Charges e.g. Fe(2+) and Fe(3+)
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Transition metals can be used as
Catalysts to speed up chemical reactions (mainly platinum and manganese)
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List the properties of transition metals (in general)
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Good conductors
Malleable
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List the properties of transition metals (in comparison to group 1 metals)
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Higher densities
- High melting points (except mercury, which is liquid at room temp.)
- Hard and mechanically strong (except mercury)
- Less reactive (don't react as vigorously)
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Why do transition metals have special properties?
A lower energy level is filled up and the third shell can hold up to 18 electrons once 2 electrons fill the fourth shell
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