A bit of Review before bonding!

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A method for communicating the location and # of electrons in electron energy levels
Shorthand uses the preceding noble gas as the “base”
Helps explain ions, magnetism, periodic table

Q 1
According to the Aufbau principle, electrons must occupy the lowest energy orbital available. From lowest to highest energy, the order of subshells is 1s, 2s, 2p, 3s,
3p, 4s, and 3d. Diagram A violates the Aufbau principle because electrons occupy subshells 2s, 2p, 3s and 3p before 1s.

Q2
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What is the maximum
# of electrons that can be found in the third electron shell?
Answer
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The 3 rd electron shell has
3 subshells: 3s, 3p, and
3d. The 3s subshell can fit 2 electrons, the 3p subshell can fit 6 electrons, and the 3d subshell can fit 10 electrons.

Q3
Atomic radii decrease from left to right across a period, because added electrons are pulled closer to the nucleus due to the increased nuclear charge.

Q4
Atomic radii increases down a group/family. As the number of electron shells increases, the distance from the outer electrons to the nucleus increases. Inner electrons shield the outer electrons, and prevent them from being pulled towards the nucleus as much.

Q5
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Which sublevel is filled after the 5s sublevel?
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A. 4p
B. 4d
C. 5p
D. 5d
Answer
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The order in which sublevels are filled can be determined by following the arrangement of elements on the periodic table. The 5s region (Rb and Sr) is followed by the
4d region (Y to Cd), moving left to right across the periodic table. The diagonal rule can also be used to determine the order for filling sublevels.

This little diagram will help you to know what order to fill up the orbitals and with how many electrons in each one. A similar one is on p. 188 of your textbook

What came next?

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Quantum Mechanics: the current theory of atomic structure based on wave properties of electrons
Heisenberg Uncertainty
Principle: it is impossible to know exact position and speed of a particle
Electron Probability
Density: a mathematical/graphical representation of the chance of finding an electron in a given space.