RC

How many valence electrons are in an atom of each element in Group 15 in the periodic table?

• 5

• 10

• 15

• 20

Answer explanation

The 5 in 15 gives you the number of valence electrons.

Tags

NGSS.MS-PS1-1

The atoms of a certain element each contain 11 protons and 1 valence electron. Which statement correctly identifies this element and describes its chemical activity?

• The element is sodium and it is highly reactive.

• The element is fluorine and it is not very reactive

• The element is sodium and it is not very reactive.

Answer explanation

The elements in group 1 / 1A are all highly reactive metals (except for hydrogen)

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

• Student 1

• Student 2

• Student 3

• Student 4

Answer explanation

The number of protons determines the identity of the atom. The number of valence electrons determines the atom's reactivity (chemical properties).

Tags

NGSS.MS-PS1-1

A chemist made the table 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 its 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 than protons.

Answer explanation

The number of valence electrons (electrons in the outer shell) determines the reactivity of an element.

Tags

NGSS.MS-PS1-1

A student drew atomic models of four elements. Based on these models which element is the least reactive?

• Neon, because it has two energy levels with eight electrons in the second level.

• Chlorine, because it has three energy levels with seven electrons in the third level.

• Gallium, because it has four energy levels with three electrons in the fourth level.

• Tin, because it has five energy levels with four electrons in the fifth level.

Answer explanation

Elements with 8 valence electrons are the least reactive elements in the periodic table.

Tags

NGSS.MS-PS1-1

An element has a metallic-grey appearance. It also has the properties of both a metal and a nonmetal. In which section of the periodic table indicated in the illustration would the element most likely be found?

• 1

• 2

• 3

• 4

Answer explanation

"Metalloids are found on the zig-zag line"

The periodic table is organized into groups and periods of elements. The characteristics of a certain group of elements are listed in the illustration. Which of these elements is in this group?

• Lithium

• Strontium

• Aluminum

• Silicon

Answer explanation

Elements with two valence electrons are found in Group 2 or 2A.

The model of an atom is shown in the illustration. An atom of which element is represented by this model?

• Boron (B)

• Carbon (C)

• Neon (Ne)

• Sodium (Na)

Answer explanation

The number of energy levels equal the period and the number of valence electrons equals the group.

Tags

NGSS.MS-PS1-1

Pick the 2 statements THAT correctly describe ELECTRONS.

• Electrons are located inside the nucleus and have a negative charge

• Electrons are located outside the nucleus and have a negative charge

• The number electrons in an atom is equal to the number of protons

• Electrons have the same mass as a proton

•   Electrons have the same mass as a neutron

Tags

NGSS.MS-PS2-3

Atoms are made up of subatomic particles called protons, neutrons and electrons.  These subatomic particles are alike in some ways and differ in other ways.  Explain some things protons and electrons have in common as well as some ways they are different.

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