Chapter Three Flashcards
Electrons and the periodic table
How do electrons orbit the nucleus
In fixed circular orbits which correspond to specific energy shells/levels of the atom
What do electron orbits of a larger radii mean
They correspond to a higher energy level
Can electrons occupy the space between energy levels
No, they can only occupy the fixed orbits
How can electrons move between energy levels
They absorb or emit energy in the form of electromagnetic radiation or light
What does ‘n’ stand for
The electron shells of an atom
As the value of n increases the energy levels
Get closer together
What did the Niels Bohr model of the atom propose
- Electrons revolve around the nucleus in circular orbits
- The electron orbits correspond to certain energy levels or shells in the atom
- Electrons can only occupy these fixed energy eves and cannot exist between two energy levels
- Electron orbits of a larger radii correspond to a higher energy level
Which electrons are involved in chemical reactions
The valence electrons (outer most electrons)
What can you predict if you know the number of valence electrons in an atom
The chemical properties of an element
How are the elements in a periodic table arranged
- In order of increasing atomic number (rows)
- The number of electrons in the outer shell of an element (columns)
Groups
- Going down in vertical columns
- Number of valence electrons in the atom of an element
- Labelled 1-18
Periods
- Across the table in rows
- Arrangement of electrons in each atom = to the number of occupied electron shells in the atom
- Labelled 1-7
Helium
- In group 18 but only has 2 valence electrons
- it is placed here however as it is unreactive
What do the elements in the same group have in common
Chemical properties
Alkali metals properties
- Highly reactive with water and oxygen
- Relatively soft metals
Halogens properties
- Coloured
- Highly reactive
Noble gases properties
- Stable
- Inert/ low reactivity
Electron configuration
The number of electrons in each shell, separated by commas starting at the shell with the lowest energy
Ion
-A positively or negatively charged atom
- When protons and electrons don’t equal the same amount
How do ions form
- Through chemical reactions or addition of energy the total number of electrons in an atom increases or decreases, this changes the electron configuration
- The electrons are gained or lost from the valence shell as they are the most weakly held electrons
Negatively charge ions
Anions
Positively charged ions
Cations