The atoms of hydrogen that are present in 7.63 g of ammonia(NH3)
find the moles of NH3 =mass/molar mass
7.63 g/ 17 g/mol = 0.449 moles
since there is 3 atoms of H in NH3 the moles of H = 0.449 x 3 = 1.347 moles
by use of 1 mole = 6.02 x10^23 atoms
what about 1.347 moles
= 1.347 moles/1 moles x 6.02 x10^23 atoms = 8.11 x10^23 atoms of Hydrogen
Explanation is in a file
bit.
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Ti2 has 2 unpaired electrons.
This problem is asking for the electron configuration of an excited atom of gallium, which according to the group it is, its excited state will theoretically be Ga³⁺, since it is a metal and loses three or less electrons, that is why it turns out positive. After writing the electron configuration, we realize the answer must be 2-8-17-4 according to the following:
<h3>Electron configurations:</h3><h3 />
In chemistry, electron configurations allow us arrange the electrons of an element according to specific energy levels and orbitals. In such a case, it turns out possible to write Gallium's electron configuration in its ground-state as follows:

However, since the given choices do not match with a charge of 3+ as formerly explained, we assume this gallium atom will be excited to 1+, due to the fact that the third energy level comprising 18 electrons, will give one to the fourth energy level, turning out in an electron configuration of:

Which matches with 2-8-17-4 as two electrons are present in the first energy level, eight in the second one, now seventeen in the third one and four in the fourth one.
Learn more about electron configurations: brainly.com/question/5524513