Elements and the Periodic Table Flashcards
How are elements represented?
By symbols with one or two letters. e.g. Cl, S
What is the atomic number?
The number of protons in an atom.
What is the mass number?
The sum of protons and neutrons in an atom.
What are isotopes?
Atoms of the same element with different numbers of neutrons.
What did Niels Bohr propose?
Electrons exist in fixed energy levels (shells).
What happens when atoms are heated?
They increase then decrease in energy emitting colored light, producing an emission spectrum.
What is the ground state of an atom?
When electrons are in their normal shells.
What is the excited state of an atom?
When electrons absorb energy and jump to higher levels.
What did Schrödinger propose?
Electrons behave as waves and exist in orbitals.
What are orbitals?
Regions where electrons are likely to be found.
What is the electron configuration for Magnesium (12)? (2)
Bohr Model: 2, 8, 2
Schrödinger Model: 1s² 2s² 2p⁶ 3s²
Q: What are the exceptions in electron filling?
A: Chromium (24) → 3d⁵ 4s¹
Copper (29) → 3d¹⁰ 4s¹
How are elements arranged in the periodic table?
By increasing atomic number.
What are groups and periods?
Groups (columns) → Same valence electrons.
Periods (rows) → Same number of electron shells.
What are the subshell blocks in the periodic table?
s-block: Groups 1-2
p-block: Groups 13-18
d-block: Transition metals
f-block: Lanthanides & actinides
What are critical elements?
Elements essential for technology and industry, some are endangered.
How can we conserve them?
Through recycling and reuse.
What is core charge?
The effective nuclear charge felt by valence electrons.
How is core charge calculated?
Core charge = Protons - Non-valence electrons
Example:
Nitrogen (7): 7 - 2 = +5
Magnesium (12): 12 - 10 = +2
What is electronegativity?
An atom’s ability to attract electrons in a bond.
What is the trend in electronegativity?
Increases across a period.
Decreases down a group.
What is atomic radius?
Distance from nucleus to valence electrons.
What is the trend in atomic radius?
Decreases across a period.
Increases down a group.
What is first ionization energy?
The energy required to remove the highest energy electron from an atom.
