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Atomic Number and Mass Number

Which element...

Question

Which element with lowest atomic number .

A

_{19} K

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B

_{24} C r

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C

_{11} N a

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D

_{29} C u

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Solution

The correct option is C $_{11} N a$
The atomic number is defined as the number of protons present in an element.

In sodium atom, the number of protons present = $11$

So, its atomic number is $11$

Which is least from the rest of the given elements.

Hence, the correct option is $C$

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Similar questions

Q. Write down the electronic configuration of the following elements from the given atomic numbers. Answer the following question with explanation.
a. ₃Li, ₁₄He, ₁₁Na, ₁₅P Which of these elements belong to be period 3?
b. ₁H, ₇N,₂₀Ca, ₁₆S, ₄Be, ₁₈Ar Which of these elements belong tot he second group?
c. ₇N, ₆C, ₈O, ₅B, ₁₃Al Which is the most electronegative element among these?
d. ₄Be, ₆C, ₈O, ₅B, ₁₃Al Which is the most electropositive element among these?
e. ₁₁Na, ₁₅P, ₁₇Cl, ₁₄Si, ₁₂Mg Which of these has largest atoms?
f. ₁₉K,₃Li, ₁₁Na, ₄Be Which of these atoms has smallest atomic radius?
g. ₁₃Al, ₁₄Si,₁₁Na, ₁₂Mg, ₁₆S Which of the above elements has the highest metallic character?
h. ₆C, ₃Li, ₉F,₇N, ₈O Which of the above elements has the highest nonmetallic character?

_{24} C r - [A r] 3 d^{5} 4 s^{1}

_{29} C u - [A r] 3 d^{10} 4 s^{1}

Why chromium and copper exhibits such electronic configuration ?

Q. Which element with lowest atomic number follows rule (b)?

Q. Complete the Table

Element	Subshell electronic configuration	No. of the outer most shell	Period number
$_{4} B e$	$1 s^{2} 2 s^{2}$	$2$	$2$
$_{6} C$	$1 s^{2} 2 s^{2} 2 p^{2}$	$2$	$2$
$_{11} N a$	$1 s^{2} 2 s^{2} 2 p^{6} 3 s^{1}$	$3$	-
$_{19} K$	$1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{1}$		-

The effective atomic number $(E A N)$ of $_{24} C r$ in $[C r (N H_{3})_{6}] C l_{3}$ is :

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