Quiz 8

Valence electrons and their importance?

Important for chemical bonding. For main-group elements, they are the outermost principal energy level. For transition elements, the outermost d electrons are counted as valence electrons. Chemical properties of an element are dependent on its valence electrons since they are held most loosely and thus can be manipulated most easily in bonding. This is why elements in the same column have similar properties (they have the same number of valence electrons.

Why do the rows in the periodic table get progressively longer as you move down the table?

You are adding sublevels as the n increases.

Effective nuclear charge? Shielding?

Z sub eff is the average or net nuclear charge

List all orbitals from 1s through 5s according to increasing energy for multi-electron atoms.

1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s. The 4s orbital fills before the 3d, and the 5s before the 4d. They are lower in energy because of greater penetration of the 4s and 5s orbitals.

What is an orbital diagram? Example?

An orbital diagram is a way of showing the electron configuration of an atom. This method symbolizes an electron as an arrow in a box that represents the orbital.

What observations led to the periodic law? What theory explains its underlying reasons?

Based on the observations that certain properties recur and certain elements have recurring properties. Quantum mechanical theory explains its existence.

What are degenerate orbitals? According to Hund's rule, how are they occupied?

Degenerate orbitals are orbitals of the same energy. In multi-electron atoms, the orbitals in a sub level are degenerate. Hund's rule states that when filling degenerate orbitals, electrons fill them singly first, with parallel spins. This is a result of an atom's tendency to find the lowest possible energy state.

Who is credited with arranging the periodic table? How are the elements arranged in the modern periodic table?

Dmitri Mendeleev. Based on the periodic law, with mass increasing from left to right and elements with similar properties fell into the same columns.

Johann Döbereiner and John Newlands

Döbereiner grouped elements into triads. Newlands organized them into octaves.

Which of the transition elements in the first transition series have anomalous electron configurations?

In the first transition series of the d block, Cr and Cu have anomalous electron configurations.

Meyer and Moseley

Meyer proposed organization based on known periodic properties. Moseley listed them by atomic number instead of atomic mass, resolving the problem with Mendeleev's table where an increase in atomic mass did not correlate with similar properties.

How to write electron configuration based on position of an element on the periodic table?

Noble gas in brackets, followed by outer electron configuration

Relationship between the properties of an element and the number of valence electrons it contains?

Properties of elements are periodic because the number of valence electrons is periodic.

Why does the s block have 2 columns, while the p block has six?

Number of columns in a block corresponds to the number of electrons that can occupy the particular sub level of that block.

What is shielding? Which electrons tend to do the most shielding?

One electron is blocked from the full nuclear charge so that the electron experiences only a partial nuclear charge. The core electrons shield the valence electrons from this full nuclear charge.

Why is electron spin important when writing electron configurations? Explain using the Pauli Exclusion Principle.

Pauli exclusion principle states that no two electrons can have the same 4 quantum numbers. Because two electrons in the same orbital have the same 3 first quantum numbers (n, l, m sub l), they must have different spin quantum numbers. This implies that each orbital can contain only two electrons, with opposite spins.

What is penetration? How does the penetration of an orbital into the space occupied by core electrons affect the energy of an electron in that orbital

Penetration occurs when an electron penetrates the 1s orbital and experiences the nuclear charge more fully. As it experiences a greater nuclear charge, according to Coulomb's law, it experiences a lower energy.

Coulomb's law? How does the potential energy of charged particles depend on the distance between charged particles and on the magnitude and sign of their changes?

Potential energy of two charged particles depends on their charges and separation. PE is positive for charges of the same sign, negative for charges of opposing signs. Magnitude of the charge is inversely dependent on the distance between the particles.

What is electron configuration?

Shows the particular orbitals occupied by the electrons in an atom. Examples: H=1s^1, Li=1s^2 2s^1

Relationship between a main group element's row number in the periodic table and the highest quantum number in the element's electron configuration. How does this relationship differ for main group elements, transition elements, and inner transition elements?

The lettered group number of a main group element is equal to the number of valence electrons for that element.

Which periodic property is important for nerve signal transmission?

The relative sizes of sodium and potassium ions is important for nerve signal transmission because the pumps and channels in cell membranes can distinguish between their size differences and allow one to pass through and not the other.

Describe the relationship between an element's row number in the periodic table and the highest principal quantum number in the element's electron configuration. How does this relationship differ for main-group elements, transition elements, and inner transition elements?

The row number of an element is equal to the highest principal quantum number of that element. However, the principal number of the d orbital being filled for transition elements is equal to the row number minus one. For inner transition elements, the f number is n-2.

Why are the sublevels within a principal level split into different energies for multielectron atoms but not for the hydrogen atom?

The sub levels within a principal level split in multi electron atoms because the outer electrons penetrate into the region of the core electrons. The sub levels of hydrogen are empty in the ground state, therefore they do not split.

Number of valence electrons for the following families, and the relationship between the number of valence electrons and the resulting chemistry of elements in the family. a) alkali metals b) alkaline earth metals c) halogens d) oxygen family

a) 1 valence electron, tend to lose it. b) 2 valence electrons, lose c) 7 valence electrons, add 1 d) 6 valence electrons, add 2

Atomic radius

consider distance between non-bonding atoms in a molecule. Decreases to right, increases down

periodic properties

properties whose values can be predicted based on the element's position on the periodic table

Label blank periodic table

s, p, d, f