Understanding the periodic table
Read the table instead of learning it by heart: deduce from an element's place its valence electrons, its number of shells, the ion it forms, whether it is a metal, its block, and compare radii and electronegativities. Every answer explains why.
- 197 cards
- 7 topics
- Free
The outline, topic by topic
Each topic is weighted the way the exam weighs it.
- Key ideas
- Valence electrons
- Electron shells
- Ions
- Metals and nonmetals
- Blocks
- Trends
A few cards from the deck
Why do noble gases react so little?
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Their outer shell is full
Two electrons for helium, eight for the others: they have nothing to gain or lose, hence their stability.
How many valence electrons does hydrogen (H) have?
- 1
- 7
- 4
- 5
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1
In the s and p blocks, the group gives the valence electrons: group 1 → 1. Its configuration: 1s¹.
Why are the alkali metals so reactive?
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They have one valence electron, easy to lose
By losing it, they reach the configuration of the previous noble gas.
Over how many shells are the electrons of lithium (Li) spread?
- 5
- 3
- 6
- 2
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2
The period number gives the number of occupied shells: period 2, group 1, so 2 shells ([He] 2s¹).
Why are the halogens so reactive?
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They are one electron short of a full shell
Seven valence electrons: gaining one gives them the next noble gas's configuration.
Which ion does lithium (Li) usually form?
- Li²⁻
- Li⁻
- Li²⁺
- Li⁺
Show the answer
Li⁺
1 valence electron: it loses 1 to reach the configuration of helium (He), a very stable noble gas.