Mass numbers of Li, Be and B are 7, 9 and 10 respectively. Which of the following has two electrons, three protons and four neutrons?

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$B^{+}$

$B e^{2 +}$

$L i^{+}$

$B e$

answer is C.

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Detailed Solution

As Li has 3 electrons. So, Li⁺, would have 2 electrons only. As atomic number of Li is 3 so number of protons will be 3 and number of the neutron = mass number - number of protons. Therefore, 7−3=4, so it would have 4 neutron

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