In the following sets of elements, indicate which element has the smallest atomic size.

a. $\mathrm{Na}, \mathrm{K}, \mathrm{Rb}$

Chlorine has two naturally occurring isotopes, ${ }^{35} \mathrm{Cl}$ (isotopic mass $34.9689 \mathrm{amu}$ ) and ${ }^{37} \mathrm{Cl}$ (isotopic mass $36.9659 \mathrm{amu}$ ). If chlorine has an atomic mass of $35.4527 \mathrm{amu}$, what is the percent abundance of each isotope?

Chlorine has two naturally occurring isotopes, $^{35} \mathrm{Cl}$ (isotopic mass = 34.9689 amu) and $^{37} \mathrm{Cl}$ (isotopic mass = 36.9659 amu). If chlorine has an atomic mass of 35.4527 amu, what is the percent abundance of each isotope?

Chlorine has two naturally occurring isotopes, ${ }^{35} \mathrm{Cl}$ and ${ }^{37} \mathrm{Cl}$. What is the mass number of each isotope? How many protons, neutrons, and electrons are present in each?

Consider a neutral atom with 30 protons and 34 neutrons. The number of electrons in this atom is?

How many protons are in an isotope of sodium with a mass number of $25$?

"The _____ of an atom is equal to the sum of the protons and neutrons in the nucleus of the atom.

a. Atomic number b. Mass number

The elements sodium, magnesium, and silicon __________.

a. are isotopes of each other

b. are in the same period of elements

c. have the same number of neutrons

d. are in the same group

e. have the same mass number

Why do the metallic elements of a given period typically have much lower ionization energies than do the nonmetallic elements of the same period?

Arrange the following sets of elements in order of increasing atomic size.

c. $\mathrm{Pb}, \mathrm{Ba}, \mathrm{Cs}, \mathrm{At}$

Arrange the following sets of elements in order of increasing atomic size.

b. $\mathrm{Rn}, \mathrm{He}, \mathrm{Xe}, \mathrm{Kr}$

Write the complete orbital diagram for element phosphorus, $Z=15$, using boxes to represent orbitals and arrows to represent electrons.

Arrange the following sets of elements in order of increasing atomic size.

a. $\mathrm{Sn}, \mathrm{Xe}, \mathrm{Rb}, \mathrm{Sr}$

In the 1920s, de Broglie and Schrödinger developed what is now called wave mechanics or quantum mechanics. Which of the following statements with regard to this model is(are) true? a. The position of an electron can be exactly found and measured. b. With the use of modern instruments, scientists can watch an electron move from point to point in its orbit. c. Energy levels in quantum mechanics are not limited to certain discrete values but are actually continuous. d. An electron has properties of a particle and a wave in this wave mechanical model of the atom.