Interim Study Guide

Henry Moseley's discovery of atomic numbers using X-ray experiments improved the organization of the periodic table by:

• allowing elements to be arranged by atomic number instead of atomic mass

• introducing the concept of isotopes

• identifying the electron configuration of elements

• discovering new elements

Atoms of elements in Group 2A of the periodic table, such as calcium, form cations by:

• gaining electrons to achieve a full outer shell

• losing electrons to achieve a full outer shell

• sharing electrons with other atoms

• neither gaining nor losing electrons

Based on periodic trends in electronegativity, identify the element among the given options that is the least electronegative and explain your choice:

• Fluorine

• Astatine

• Lithium

• Francium

In Rutherford's gold foil experiment, what conclusion did Rutherford draw about the atom's structure based on the observation that some alpha particles were deflected while most passed through?

• The atom is a solid mass with no empty space.

• The atom has a dense nucleus with electrons orbiting around it.

• The atom is composed mostly of empty space with a small, dense nucleus.

• The atom is a uniform distribution of positive and negative charges.

Neutrons are located within an atom in the:

• nucleus

• electron cloud

• outer shell

• proton layer

The relationship between energy and wavelength is described by which of the following?

• Energy is directly proportional to wavelength.

• Energy is inversely proportional to wavelength.

• Energy and wavelength are unrelated.

• Energy is equal to wavelength.

Calculate the atomic mass of an element with three isotopes, given their atomic masses (23.99 amu, 24.99 amu, and 25.98 amu) and their respective relative abundances (78.99%, 10.00%, and 11.01%).

• 24.31 amu

• 24.00 amu

• 25.00 amu

• 24.50 amu

Determine the electron configuration of a calcium atom (atomic number 20).

• 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

• 1s² 2s² 2p⁶ 3s² 3p⁶ 3d²

• 1s² 2s² 2p⁶ 3s² 3p⁶ 4p²

• 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s¹

Compare the electronegativity of two elements, one located near the top right and the other near the bottom left of the periodic table. What type of bond is likely to form between them?

• Ionic bond

• Covalent bond

• Metallic bond

• Hydrogen bond

Provide the correct chemical formula for dinitrogen pentoxide.

• N2O5

• NO2

• N2O3

• N2O