Hello!
To find the mass of helium, we need to multiply the total moles by the mass of helium. We are given 2.714 moles of helium, and the mass of helium is about 4.00 grams. Now, we multiply the two values together to get the grams.
2.714 moles x 4.00 grams = 10.856 grams
According to the number of significant figures, 2.714 moles of helium has a mass of 10.9 grams (exact value: 10.856 grams).
Answers:
(a) 1s² 2s²2p³; (b) 1s² 2s²2p⁶ 3s²3p⁶ 4s²3d²; (c) 1s² 2s²2p⁶ 3s²3p⁵
Step-by-step explanation:
One way to solve this problem is to add electrons to the orbitals one-by-one until you have added the required amount.
Fill the subshells in the order listed in the diagram below. Remember that an s subshell can hold two electrons, while a p subshell can hold six, and a d subshell can hold ten.
(a) <em>Seven electrons
</em>
1s² 2s²2p³
There are two electrons in the 2s subshell and three in the 2p subshell. The remaining two electrons are in the inner 1s subshell.
(b) <em>22 electrons
</em>
1s² 2s²2p⁶ 3s²3p⁶ 4s²3d²
There are two electrons in the 4s subshell and two in the 2p subshell. The remaining 18 electrons are in the inner subshells.
(c) <em>17 electrons</em>
1s² 2s²2p⁶ 3s²3p⁵
There are two electrons in the 3s subshell and five in the 2p subshell. The remaining 10 electrons are in the inner subshells.
The reasonable ground-state electron configuration is: 1s2 2s2 2p6 3s2 3p6 4s2 4d8
HNO3 + Ca —-> H2O + N20 + Ca(NO3)2
