Unit 02 Review

Which element is a noble gas?

• Krypton

• Oxygen

• Vanadium

• Calcium

Answer explanation

Elements in Group 18 are the noble gases, and krypton is the only element in Group 18.

Tags

NGSS.HS-PS1-1

Compared to a neon atom, a helium atom has a —

• greater number of electrons.

• larger atomic number.

• smaller atomic radius.

• lower first ionization energy.

Answer explanation

Since the helium atom is above the neon atom, it has a smaller atomic radius.

Neon has more electrons, a larger atomic number, and a lower first ionization energy.

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Which of the following is a physical property that Mendeleev used to design the periodic table?

• Reactivity

• Oxidation state

• Atomic mass

• Structure

Answer explanation

Mendeleev used relative atomic mass to organize the periodic table of the elements.

The modern model of the atom shows that electrons are —

• found in regions called orbitals.

• in the nucleus with neutrons.

• orbiting the nucleus in fixed orbits.

• located in a solid sphere around the nucleus.

Answer explanation

Although all of the choices existed at one time, the modern model of the atom has electrons existing in 'clouds' (called orbitals) around the nucleus,

Visible light occupies the range of wavelengths from 380 to 790 nanometers in the electromagnetic spectrum. Which of the following kinds of electromagnetic radiation has shorter wavelength than visible light?

• x-rays

• infrared

• radio waves

• microwaves

Answer explanation

Wavelength decreases as you from left to right across the electromagnetic spectrum. X-rays are to the right of visible light on the spectrum.

An atom of neon in the ground state tends not to bond with an atom of a different element because the neon atom has —

• more neutrons than protons.

• a total of two valence electrons.

• more protons than neutrons.

• a total of eight valence electrons.

Answer explanation

Since neon is in Group 18 it has 8 valence electrons and very stable electron structure.

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Which of these elements has atoms with the largest atomic radius?

• Sr

• Ba

• Rb

• Cs

Answer explanation

The atomic radius increases as you move down a group. Since Cs is at the bottom of the groups (and to the left of Ba), it has the largest atomic radius.

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Which element has properties most similar to those of fluorine?

• S

• Ne

• Cl

• Ar

Answer explanation

Elements in the same family have similar properties. Since Cl is also in Group 17, it will have properties similar to F.

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NGSS.HS-PS1-2

As the elements in Group 17 on the Periodic Table are considered from top to bottom, what happens to the atomic radius and the metallic character of each successive element?

• The atomic radius and the metallic character both decrease.

• The atomic radius and the metallic character both increase.

• The atomic radius increases, and the metallic character decreases.

• The atomic radius decreases, and the metallic character increases.

Answer explanation

The atomic radius increases as you move down a group. Although Group 17 elements are nonmetals, the metallic character still increases as you move down a group.

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Scientists before Mendeleev had observed that certain elements reacted similarly with other chemicals. Which further observation led Mendeleev to create the periodic table?

• The elements within these groups often differed in physical properties, such as color and texture.

• Elements that did not fit in these groups belonged in the lanthanide and actinide series.

• The atomic weights of the elements within these groups were spaced at nearly regular increments.

• The reactivity of the elements within these groups varied at nearly regular increments.

Answer explanation

As Mendeleev continued to study elements he noticed repeating patterns at regular increments.

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