CC4 Flashcards
Why did Mendeleev leave gaps in his periodic table?
Mendeleev assumed that elements would continue to be discovered, so he left gaps for them.
What did Mendeleev use gaps in his periodic table for?
Mendeleev used the gaps in his table to make predictions about the properties of undiscovered elements, based on the properties of nearby elements.
What did Henry Moseley discover?
Moseley showed that an elements atomic number was a physical property of an elements atoms. He fired high-energy electrons at different elements, which made them give off X-rays. He discovered that for every step increase in atomic number, there was a step change in the energy of these X-rays.
What did Moseley realize about the atomic number?
He realized that an atomic number was equal to the number of positive charges in the nucleus of an atom. This meant that the atomic number must be the number of protons in a nucleus.
What is the electronic configuration?
The arrangement of electrons in shells around the nucleus of an atom.
What is the arrangement of electronic configuration for elements?
- The first shell can contain up to two electrons.
- All the remaining shells can contain up to eight electrons.
How can electronic configuration be written?
It can be written in a number format (e.g. the electronic configuration for sodium is 2.8.1 meaning there are 11 electrons total).
How can you use the periodic table to work out electronic configuration?
You can work out the electronic configuration of an element from its atomic number (e.g. The atomic number for chlorine is 17 - each chlorine atom contains 17 protons and so also contains 17 electrons).
How is the electronic configuration of an element related to its position in the periodic table?
- The number of electron shells is equal to the period number (across the table).
- The number of electrons in the outer shell is equal to the group number, except for group 0 elements, which all have full outer shells (down the table).
