Describe the trends in electron configuration in the periodic table by selecting the terms from the drop-down menus. The number of valence electrons
from the left to right across a period.
The number of valence electrons
from the top to the bottom of a group.
Electrons are added into the outermost
in Groups 1 and 2.
Electrons are added in the outermost
in Groups 3 through 12.
Electrons are added in the outermost
in Groups 13 through 18.

Asingle atom of an element has 21 neutrons, 20 electrons, and 20 protons. which element is it? ok o z

Astudent is given a sample of a blue copper sulfate hydrate. he weighs the sample in a dry covered porcelain crucible and got a mass of 23.875 g for the crucible, lid, and sample. the mass of the empty crucible and lid was found earlier to be 22.652 g. he then heats the crucible to expel the water of hydration, keeping the crucible at red heat for 10 minutes with the lid slightly ajar. on colling, he finds the mass of crucible, lid, and contents to be 23.403 g. the sample was changed in the process to very light clue anhydrous cuso4. if there are again 100.0 g of hydrate, how many grams of cuso4 are in it? how many moles of cuso4? (hint: molar mass of cuso4 = 159.6 g / mole. what per cent of the hydrate is cuso4? you may convert the mass of cuso4 to moles.)

If you add 5.00 ml of 0.100 m sodium hydroxide to 50.0 ml of acetate buffer that is 0.100 m in both acetic acid and sodium acetate, what is the ph of the resulting solution? acetic acid: ka = 1.8. x 10-5