The Periodic Table Flashcards
How did scientist try to classify elements in the 19th century?
Based on properties and atomic weights
What did new land propose in 1863?
His law of octaves; similar properties are repeated every eighth element, he put the elements know at the time into 7 groups based on atomic weight.
Why were new lands ideas not accepted
After calcium the properties did not match very well within the groups
Why was mendeleevs table better than newlands
The elements fitted better in the groups as he left gaps for undiscovered elements
Why did scientists readily accept mendeleevs ideas?
He predicted the properties of missing elements and these were confirmed when the elements were discovered
What did scientist know and not know in the 19th century?
They had discovered many elements but did not know about the structure of the atom
When did scientists find out about protons and electrons?
The start of the 20th century
Why do elements in the same group have similar chemical properties?
They have the same number of electrons in their highest energy level
How are the elements arranged now?
In order of increasing atomic number and are arranged in vertical groups
Within a group what does the reactivity depend on?
The total number of electrons
Going down the group, there are ……… Energy levels occupied and so the atoms get …….
More
Larger
As the atoms get larger what happens to the attraction between the nucleus and the electrons in the highest occupied energy level?
The electrons in the highest occupied energy level are less strongly attracted to the nucleus
What is the trend in reactivity of metals?
The reactivity of metals increases going down the group
How do metals react
By losing electrons
Why do metals get more reactive going down the group
To react, metals lose electrons. As the atoms get larger there are more occupied energy levels and the electrons in the highest occupied level are less strongly attracted by the nucleus and so are lost more easily
How do non metals react
Gaining electrons
What is the trend in reactivity of non metals
The reactivity decreases down the group
Why does the reactivity of non-metals decrease going down the group
As you go down the group, the number of occupied energy levels (filled shells) increases. The higher the energy level of the outer electrons, the greater the distance from the nucleus, and the less easily electrons are gained. This is why elements in Group 7 become less reactive as you go down the group
What are group 1 elements called
Alkali metals
What do the alkali metals react readily with
Air and water
What are the boiling points & melting points of alkali metals like
They are soft solids at room temperature with low melting and boiling points that decrease down the group
What are the densities of alkali metals like
Low
What do alkali metals produce when reacting with water
Hydrogen and metal hydroxides
What do alkali metals react with to form colourless salts
The halogens
What do alkali metals dissolve in water to form
Solutions that are colourless
Why does reactivity increase going down the group of the alkali metals
Because the outer electron is less strongly attracted to the nucleus as the number of occupied energy levels increases and the atoms get larger
Why is think less reactive than sodium
Lithium atoms are smaller than sodium, they have fewer occupied energy levels. Their outer electron is more strongly attracted by the nucleus and so is less easily lost when they react
What are the boiling and melting points of transition metals like compared to alkali metals
Except for Mercury they have higher mp and bps
What 3 properties do transition metals have
Malleable
Ductile
Good conductors of heat and electricity
What are metal reactions like
Slow, not at all or with air or water at normal temperatures
How are metals often used
Most are strong and dense and are useful as building materials, often as alloys
What are the charges of the transition metals
Positive ions with various charges
What do metal compounds look like
Brightly coloured
What else are transition metals and their compounds used for in chemical reactions
Catalyst
Why do halogens have low bps and MPs
They have small molecules
How do the bps and MPs change in the group
They have low bps and mps which increase going down the group
What colour is fluorine what state
Pale yellow gas
What colour is chlorine what state
Green gas
What colour is bromine and what state
Red-brown liquid
What state and colour is iodine
Grey solid which easily baptised to a violet gas
What is formed when halogens ironically bond
They form halide ions with a - charge
What is formed when halogens covalently bond
Molecules are formed
What is the reactivity trend in the halogen group
Reactivity decreases going down the group
A …… Reactive halogen is able to …….. A ………. Reactive halogen from an …….. Solution of a halide compound
More
Displace
Less
Aqueous
Why does the reactivity decrease going down group 7
The attraction of the outer electrons to the nucleus decelerates as the number of occupied energy levels increases
