# Chemistry - Periodic table

What is the relative atomic mass?
Average mass of different isotopes. It's also based on how common each isotope is.
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Why do some elements in the periodic table have a mass number of x.5?
They're isotopes so they have different mass numbers so use the relative atomic mass. (e.g. Cl has mass number 35.5, and has two isotopes of mass 35 and 37. Th reason it's closer to 35 is because that isotope is more common)
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How can you work out Relative atomic mass?
(Mass# x %abundance of isotope 1)plus(same with isotope 2) divided by 100
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Boron has two common isotopes. Mass number's = 10(20 abundance) and 11(80 abundance). Atomic number= 5. What's the relative atomic mass?
(20x10)plus(80x11) = 1080. divided by 100= 10.8
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The third shell in an atom can hold 8 electrons, the fourth can hold ___
18
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The number of electrons can be written in the form [x,y], each number reprenting the electrons in a shell. Write this for Carbon (atmoic# = 6)
[2,4]
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Element Ne has 10 electrons [2,8], meaning it has a full outer shell. What group would Ne be in?
Group 0 as they're 0 extra electrons in the outer shell, as it's full/completed.
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What is group 0 also known as?
The noble gases.
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What group is Na in? (atomic# =11)
[2,8,1] group 1.
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What are the block of elements between group 2 and 3 called?
Transition elements
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All the elements in a group have ____ properties.
Similar properties.
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Why is this?
They all have same number of electrons in outter shell.
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John Newlands arranged the elements in ___ ____ ___
Increasing atomic mass
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By doing this, what did he notice?
Every 8th element reacted in a similar way?
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He called this the law of ___
Octaves
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Beacuse he always ordered them by mass, some elements were grouped together with different properties.
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## Other cards in this set

### Card 2

#### Front

Why do some elements in the periodic table have a mass number of x.5?

#### Back

They're isotopes so they have different mass numbers so use the relative atomic mass. (e.g. Cl has mass number 35.5, and has two isotopes of mass 35 and 37. Th reason it's closer to 35 is because that isotope is more common)

### Card 3

#### Front

How can you work out Relative atomic mass?

### Card 4

#### Front

Boron has two common isotopes. Mass number's = 10(20 abundance) and 11(80 abundance). Atomic number= 5. What's the relative atomic mass?

### Card 5

#### Front

The third shell in an atom can hold 8 electrons, the fourth can hold ___