Lithium has an atomic number of 3 and a mass number of 7. Which of the following is the number of neutrons in a lithium atom?
A. 4
B. 7
C. 12
D. 3
The atom is identified by the atomic number in the periodic table. The atomic number is equal to the number of protons and mass number is the sum of the number of protons and neutrons in the nucleus of an atom. Thus, to find how many neutrons are in lithium atom we use the formula below.
Mass number = number of protons + number of neutrons.
Letting n be number of neutrons in the lithium atom, we have
7=3+n
Rearranging the above equation
3+n=7
n=7-3
n=4
Thus, lithium atom has 4 neutrons.
Therefore, the Correct Answer is A.
More Questions on TEAS 7 Science
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Q #1: Which of the following are structural features of the trachea?
A. C-shaped cartilage
B. Smooth muscle fibers
C. Cilia
D. All of the above
Answer Explanation
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Q #2: Which of the following sequences on a DNA molecule would be complementary to GCTTATAT?
A. TAGGCGCG
B. ATCCGCGC
C. CGAATATA
D. TGCCTCTC
Answer Explanation
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Q #3: Nitrogen gas is an extremely stable molecule because its structure contains which of the following?
A. Resonance bonds
B. Ionic bonds
C. Triple covalent bonds
D. Hydrogen bonds
Answer Explanation
The Lewis structure of nitrogen gas is shown below. Triple bonds are stronger than double or single bonds. Therefore, we can infer that the triple bond between the two nitrogen atoms makes nitrogen gas more stable.
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Q #4: Metabolism of proteins Which of the following substances is excreted by sweat glands in response to the breakdown of proteins and the formation of ammonia?
A. Sebum
B. Urea
C. Lysozymes
D. Water
Answer Explanation
Proteins are nitrogen-based compounds, which when broken down release ammonia. Ammonia is a toxic substance to the body, and sebaceous glands coverts it to urea.
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Q #5: Base your answer on the graph and on your knowledge of biology. Which is a true statement about the relationship between pH and enzyme action?
A. All enzymes work best at a neutral pH.
B. Adding more acid does not affect the rate of activity of an enzyme.
C. Enzymes function only in a pH range of 4.0 to 5.5.
D. The activity of an enzyme is affected by pH.
Answer Explanation
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Q #6: Which of the following are used to determine a person’s DNA sequence?
A. Genes
B. Enzymes
C. Hormones
D. Blood types
Answer Explanation
A gene is the basic physical and functional unit of heredity and it is the DNA that make up genes. Enzymes are biological catalysts that speed up metabolic and cellular reactions in our bodies. Hormones are responsible for controlling the action of certain cells or organs in our bodies. Blood types are of four types, A, B, AB, and O.
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Q #7: Which of the following best describes veins?
A. thick walled, small lumens, low pressure, lack valves
B. thin walled, large lumens, low pressure, have valves
C. thin walled, small lumens, high pressure, have valves
D. thick walled, large lumens, high pressure, lack valves
Answer Explanation
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Q #8: Which of the following processes causes most of the carbon dioxide from the blood to move into the alveoli?
A. Diffusion down a concentration gradient
B. Conversion of carbon monoxide
C. Passive transport using carrier proteins
D. Active transport using energy
Answer Explanation
Carbon dioxide moves from the blood to the alveoli through the process of diffusion. The blood has a high concentration of carbon dioxide than the alveoli.
Therefore, carbon dioxide diffuses from blood to alveoli through the cell membrane. -
Q #9: Which of the following is the atomic number of an atom that has 12 protons and 12 neutrons?
A. 144
B. 12
C. 24
D. 1
Answer Explanation
elements are arranged on the periodic table based on their atomic number. This identity is critical in evaluating the chemical families of elements in chemistry. Atoms are made of protons, neutrons, and electrons. Protons and neutrons are found in the nucleus while electrons are found outside the nucleus of the atom. It is the number of protons of an atom that gives its atomic number. Therefore, an atom with 12 protons has an atomic number of 12.
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Q #10: Punnett square In a certain plant, red flowers are dominant over white flowers. A plant heterozygous for red flowers and a plant with white flowers are crossed. Which of the following is the expected proportion of phenotypes in the next generation?
A. 4 red, 0 white
B. 2 red, 2 white
C. 1 red, 3 white
D. 3 red, 1 white
Answer Explanation
We use the Punnet square to find the population of the resulting offspring from the crossing of a plant heterozygous for red flowers with a plant with white flowers.
Let R be the dominant allele for red while r is the recessive allele color for red. Therefore, the phenotype for parent 1 which is heterozygous for red flower will be Rr and the second parent with white flowers will be rr.
We cross the two phenotypes in a Punnet square as follows
r
r
R
Rr
Rr
r
rr
rr
Thus, there are 2 heterozygous offspring with red flowers and 2 offspring with white flowers.
