Atom X has 17 protons. How many electrons are in its valence shell?
10
3
5
7
The Correct Answer is D
A. 10: If atom X has 17 protons, it is chlorine. Its total electrons in the neutral state are also 17. Having 10 electrons in the valence shell would be impossible, since the outermost shell of chlorine can hold only up to 8 electrons.
B. 3: Three valence electrons are characteristic of elements in Group 13, such as aluminum. Chlorine belongs to Group 17, so it does not have three electrons in its outer shell.
C. 5: Five valence electrons correspond to elements in Group 15, such as nitrogen or phosphorus. Since chlorine is in Group 17, it cannot have five electrons in its valence shell.
D. 7: Chlorine has an electron configuration of 1s² 2s² 2p⁶ 3s² 3p⁵, which totals 7 electrons in its outermost shell. This matches its placement in Group 17, making 7 the correct number of valence electrons.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. To keep the body's blood sugar level high: Negative feedback does not aim to maintain a specific high level of blood sugar. Instead, it responds to deviations from a set point, whether high or low, to restore balance.
B. To regulate excretion via the kidneys: While kidney function can be influenced by negative feedback mechanisms, this is a specific example rather than the overall result of negative feedback in the body.
C. To control body movement: Body movement is largely coordinated by the nervous and muscular systems. Negative feedback primarily regulates physiological variables rather than directly controlling voluntary movement.
D. To maintain homeostasis: Negative feedback mechanisms counteract changes in the body’s internal environment, returning physiological variables to their set points. This constant regulation helps maintain stable conditions necessary for survival.
Correct Answer is A
Explanation
A. Urinary system: The urinary system, including the kidneys, ureters, bladder, and urethra, filters blood to remove metabolic waste, regulates fluid volume, controls electrolyte levels, and maintains acid-base balance. It also influences blood pressure through the renin-angiotensin-aldosterone system.
B. Cardiovascular: The cardiovascular system transports blood, nutrients, gases, and waste products throughout the body, but it does not directly eliminate waste or regulate electrolytes and acid-base balance.
C. Digestive system: The digestive system breaks down food, absorbs nutrients, and eliminates solid waste, but it does not play a primary role in regulating blood pressure or electrolyte balance.
D. Immune system: The immune system defends the body against pathogens and foreign substances but does not manage waste elimination, electrolyte balance, or blood pressure.
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