Category 2

(8.5A) An atom has 25 protons, 30 neutrons, and 25 electrons. What is the charge of the atom's nucleus?

• +25
• +30
• -25
• -30

(8.5B) An atom of which element is represented by this model?

• Boron (B)
• Carbon (C)
• Neon (Ne)
• Sodium (Na)

(8.5C) A researcher wants to experiment with an element that reacts like phosphorous (P) but has a greater atomic mass. Which element should the researcher select for the experiment?

• Nitrogen (N)
• Sulfur (S)
• Arsenic (As)
• Silicon (Si)

(8.5C) 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

(7.6A) Hay is made up of organic compounds. What are the main elements in many organic compounds?

• Helium, carbon, sodium
• Sodium, hydrogen, nitrogen
• Carbon, hydrogen, oxygen
• Radon, oxygen, helium

(8.5B) The atoms of a certain element each contain 11 protons and 1 valence electron. Which statement correctly identifies this element and describes its chemical reactivity?

• The element is sodium, and it is highly reactive.
• The element is flourine, and it is not very reactive.
• The element is sodium and it is not very reactive
• The element is flourine, and it is highly reactive

(8.5D) In which of these compounds are there twice as many oxygen atoms as hydrogen atoms?

• H₃PO₄
• H₂SO₄
• HClO₃
• H₂O

(6.5C) The chemical equation shown below represents a reaction that produces fuel for certain cars.
CO + H₂O ---> CO₂ + H_{2
Which of these represents an element?}

• CO
• H₂O
• CO₂
• H₂

(8.5D) Serotonin is a chemical substance that acts as a neurotransmitter. It helps relay messages in the human brain. The formula for one molecule of serotonin is shown below.
C₁₀H₁₂N₂O
How may atoms in all are in a molecule of serotonin? 

• 10
• 25
• 24
• 100

What is the number of protons that the element in this image contain?

• 14
• 7
• 15
• 18