Science STAAR 8.5 b-c

A chemist made the table below to record some atomic properties of four elements.

Based on the information in the table, which conclusion about the chemical reactivity of these elements is valid?

• Boron is the most reactive because it has the most protons.

• Fluorine is the most reactive because it has 7 electrons in the outer shell.

• Silicon is the most reactive because it has an equal number of protons and neutrons.

• Gallium is the most reactive because it has many more neutrons that protons.

Four students were asked to name the parts of an atom that determine the atom's identity and chemical properties. The students' responses are shown in the table below. Which student's responses are correct?

• Student 1

• Student 2

• Student 3

• Student 4

Tin, Sn, is a soft white metal. It has a low melting point compared with other metals. Tin is widely used as a coating for cans of food. Which statement accurately describes atoms of tin?

• Tin atoms have 50 protons.

• Tin atoms have five valence electrons.

• Tin atoms have 119 neutrons.

• Tin atoms have 68 electrons.

A chemist is identifying the elements present in a sample of seawater. What characteristic of an element's atom always determines the element's identity?

• The number of protons

• The number of neutrons

• The location of valence electrons

• The number of valence electrons

A student is studying calcium, a highly reactive element that humans need for strong bones. Which characteristic of calcium is most closely related to its chemical reactivity?

• The 20 protons in each atom of calcium

• The density of calcium, which is 1.54 g/cm³

• The atomic mass of calcium, which is 40.078 amu

• The 2 valence electrons in each atom of calcium

When trying to identify an unknown element, a scientist determines what other elements the unknown element reacts with chemically. Which property of the unknown element determines the other elements it reacts with?

• The total number of neutrons in the unknown element

• The total number of particles in the nucleus of the unknown element

• The number of protons in the nucleus of the unknown element

• The number of valence electrons in the unknown element

The table below lists three characteristic of an atom of an element. An atom of which element is described by the data in the table?

• Radon (Rn)

• Cadmium (Cd)

• Rubidium (Rb)

• Astatine (At)

An atom of which element is represented by this model?

• Boron (B)

• Carbon (C)

• Neon (Ne)

• Sodium (Na)

Which pair of properties describes the elements in Group 18?

• They are chemically stable and liquid at room temperature.

• They have eight valence electrons are are flammable.

• They are magnetic and boil at low temperatures.

• They are gaseous at room temperature and chemically stable.

A researcher wants to experiment with an element that reacts like phosphorus (P) but has a greater atomic mass. Which element should the researcher select for the experiment?

• Nitrogen (N)

• Sulfur (S)

• Arsenic (As)

• Silicon (Si)