C3.1 Periodic Table Flashcards
What did Newland suggest about the periodic table?
- He noticed after arranging the atoms in order of atomic mass that every 8th element had similar properties - “Law of Octaves”
- Suggested arranging them in octaves (called Newman’s Octaves)
Why were atoms arranged in atomic mass in the early 1800s?
There was no such thing as atomic number as atomic structure (e.g protons and electrons) were unknown.
What were the problems with Newland’s idea (3 points)?
- Some of his groups contained elements with no similar properties
- It left no gaps for undiscovered elements
- He mixed up metals and non-metals
What did Mendleev suggest about the periodic table?
- Created “the table of elements”
- Put them in order of atomic mass (like Newland)
- Found he had to leave gaps to keep elements with same properties in the same groups (vertical columns)
- Gaps predicted properties of undiscovered elements at the time.
When did scientists finally accept the periodic table?
When Mendleev’s predictions from the gaps he left were proven true by newly discovered elements
How did scientists attitude towards the periodic table change over time (three steps)?
Scientists regarded the periodic table:
- First as a curiosity : when there was no evidence for it
- Then as a useful tool : when Mendleev was proven right) - And finally as an important summary of the structure of atoms : when atomic structure was discovered and it fit with the periodic table
How are elements in the modern day periodic table arranged?
By order of atomic number (after the discovery of atomic structure)
How are groups arranged?
Into columns by the number of electrons in the outer shell
What does the group number tell you?
The amount of electrons in the outer shell
How are periods arranged?
Into rows by the number of shells of electrons
What is Group 1 of the periodic table known as?
The alkali metals
What are the trends as you go down the alkali metals group (2) ?
The lower down, the higher the reactivity and the lower the melting/boiling points
What are the first three metals of the group 1?
Lithium, Sodium, Potassium
What are the properties of the alkali metals (2) ?
- Low density (first three less dense than water)
- Very reactive (only one outer electron)
Why is alkali metals more reactive the further you go down the group?
- The further you go down, the more shells between the nucleus and the outer shell with one electron, as well as there being more distance between it and the nucleus
- The other electrons in the shell shield the nucleus’s positive attraction to the electron and repel the electron with negative charge.
- This means it is easier to lose the electron, making it more reactive.
How do alkali metals react with water?
- Vigorously, they fizz and float around on the surface.
- Produce hydrogen
- Form hydroxides which dissolve in water to form alkali solutions.
How do alkali metals react with non-metals?
- They form ionic bonds.
- White compounds are formed which dissolve in water to make colourless solutions.
What is group 7 of elements known as?
The Halogens
What are the trends as you go down the halogens group (2) ?
- The more you go down, the less reactive.
- The more you down, the higher the melting/boiling point.
Why is halogens less reactive the further you go down the group?
- The further you go down, the more shells between the nucleus and the outer shell as well as there being more distance between it and the nucleus
- The other electrons in the shell shield the nucleus’s positive attraction to the shell and repel it with negative charge.
- This means it is harder to gain another electron as there is less attraction.
What are the first four elements of the halogen group?
Flourine, chloride, bromine, iodine
What are the properties of fluorine?
Very reactive, poisonous yellow gas
What are the properties of chlorine?
Fairly reactive, poisonous dense green gas
What are the properties of bromine?
Dense, poisonous, red-brown volatile liquid
What are the properties of iodine?
Dark grey, crystalline solid, purple vapour
How do halogens react with metals?
They form negative ions - halides
Describe displacement in the halogen group.
More reactive halogens can replace less reactive ones in their salt solutions e.g chlorine can replace bromine in bromide.
List the properties of the transitional metals in comparison to alkali metals.
- Much denser, shinier, harder and stronger.
- Much higher melting points (except mercury)
- Much less reactive - not as vigorous with water & oxygen
What property do transitional metal ions have?
Each metal has more than one with different charges
What property do transitional metal compounds have?
They all have different colours
What are transitional metals and their compounds useful for?
They make good catalysts
Why are alkali metals known as that?
They have a PH more than 7 when reacted with water
