Multiple Choice
Which of the following elements is a transition metal?
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4. Atoms and Elements
Periodic Table: Representative Elements & Transition Metals
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An element has 25 electrons (i.e., atomic number ). Which classification best describes this element in the periodic table?
A
Halogen
B
Representative element (a main-group s- or p-block element)
C
Transition metal (a d-block element)
D
Noble gas
Verified step by step guidance1
Identify the atomic number of the element, which is given as 25. The atomic number corresponds to the number of protons and, in a neutral atom, also the number of electrons.
Recall the layout of the periodic table: elements are arranged in blocks based on their electron configurations. The s-block includes groups 1 and 2, the p-block includes groups 13 to 18, the d-block includes transition metals (groups 3 to 12), and the f-block includes lanthanides and actinides.
Determine the position of the element with atomic number 25 by considering its electron configuration. The first 20 electrons fill the first four energy levels, and the 21st to 30th electrons start filling the 3d subshell, which corresponds to the d-block.
Since the element with 25 electrons has electrons filling the 3d subshell, it belongs to the d-block, which is characteristic of transition metals.
Conclude that the element with atomic number 25 is classified as a transition metal, not a halogen, representative element, or noble gas.
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