8th Grade Science Final Exam Review

What is the difference between the number of electrons in an atom of selenium, Se, and the number of electrons in an atom of aluminum, Al?

How many protons, neutrons, and electrons are present in an atom of hafnium, Hf, with a mass number of 178?

• 72 protons, 178 neutrons, 106 electrons
• 72 protons, 106 neutrons, 72 electrons
• 178 protons, 250 neutrons, 72 electrons
• 106 protons, 72 neutrons, 106 electrons

Tags

NGSS.MS-PS1-1

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

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NGSS.MS-PS1-1

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 than protons.

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NGSS.MS-PS1-1

A student is studying the ways different elements are similar to one another. Diagrams of atoms from four different elements are shown below. Which two atoms are of elements in the same group in the periodic table?

• Atom 1 and Atom 2

• Atom 1 and Atom 4

• Atom 2 and Atom 3

• Atom 3 and Atom 4

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NGSS.MS-PS1-1

Which two elements on the periodic table are in the same period?

• Sn and Rb
• F and Cl
• K and Ba
• Se and Te

In which of these compounds are there twice as many oxygen atoms as hydrogen atoms?

• H₃PO₄

• H₂SO₄

• HClO₃

• H₂O

Tags

NGSS.MS-PS1-1

Which of these formulas contain equal numbers of nitrogen atoms?

• Formulas I and III

• Formulas I and IV

• Formulas II and III

• Formulas I, II, and V

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NGSS.MS-PS1-1

Coal contains carbon and other elements. Carbon dioxide forms when coal burns in the presence of oxygen. Which of these is the best evidence that a chemical reaction occurs when coal burns?

• The shape of the coal changes.

• Oxygen is present.

• A new substance is produced

• Coal is made up of more than one element.

Tags

NGSS.MS-PS1-2

Nitrogen dioxide is a gas that can be generated by emissions from vehicles and factories. It can also be generated by natural sources, such as forest fires, lightning, and microbial activity in soil. The equation for producing nitrogen dioxide is shown below. Which of these provides evidence that a chemical reaction occurs?

• A gas is present.

• The total number of atoms remains unchanged.

• The state of matter remains the same.

• A brown gas is produce

Tags

NGSS.MS-PS1-2