Answer:
The electron configuration for calcium is: 1s2 2s2 2p6 3s2 3p6 4s2. Since calcium is in the fourth row and the second column of the s-block on the periodic table of elements, its electron configuration ends in 4s2. Every lower orbital is filled, starting with the 1s orbital.
Explanation:hope this helps
Answer:

Explanation:
<u>1. Convert Atoms to Moles</u>
We must use Avogadro's Number: 6.022*10²³. This is the number of particles (atoms, molecules, ions, etc.) in 1 mole of a substance. In this case, the particles are atoms of helium. We can create a ratio.

Multiply by the given number of helium atoms.

Flip the fraction so the atoms of helium cancel.



<u>2. Convert Moles to Grams</u>
We must use the molar mass, which is found on the Periodic Table.
Use this as a ratio.

Multiply by the number of moles we calculated. The moles will then cancel.



<u>3. Round </u>
The original measurement has 3 significant figures (5, 5, and 0). Our answer must have the same. For the number we calculated, it is thousandth place. The 3 in the ten thousandth place tells us to leave the 5.

The mass is <u>0.365 grams of helium</u> so choice A is correct.
Explanation:
Because the solution only contains Na+ and Cl− ions, and water, and not the metal Na(s) . You cannot evaporate the water from the solution and hope to obtain anything but NaCl(s) .
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Na(s) has an electron configuration of 1s^2 2s^2 2p^6 3s^1 , but Na+(aq) has an electron configuration of 1s^2 2s^2 2p^6 . That means they are not the same element, and thus, there is no straightforward way of extracting Na(s) from a NaCl (aq) solution
First, let's state the chemical reaction:

We can find the number of moles of Cl2 required to produce 0.0923 moles of AlCl3, doing a rule of three: 3 moles of Cl2 reacted produces 2 moles of AlCl3:

The calculation would be:

And the final step is to convert this number of moles to grams. Remember that the molar mass can be calculated using the periodic table, so the molar mass of Cl2 is 70.8 g/mol, and the conversion is:

The answer is that we need 9.770 grams of Cl2 to produce 0.0923 moles of AlCl3.
Answer:
Above the Curie temperature, a magnet permanently loses all or some of its magnetism. External magnetic fields: Strong, opposing magnetic fields can cause the magnetic domains to lose their orientation and relax into a lower state of energy where they are not aligned.
Explanation: