The answer to this question would be: <span>D. Magnesium
The </span><span>number of energy levels of aluminum is 3 which was why it was put on the 3rd row. The valence of calcium is 2 which is why it was put in the 2nd column. If you look at the periodic table, the answer should be clear that it was magnesium.</span>
We are asked to convert the value <span>72 kilometers per hour to units of meters per second. We need conversion factors to multiply to this value. We convert as follows:
</span><span>72 km / hr ( 1000 m / 1 km ) ( 1 hr / 3600 s ) = 20 m/s --->OPTION B</span><span>
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Your answer is B and the element is Carbon
So what your looking for is matching isotopes. Isotopes are elements that are the same in amount of protons but different in mass meaning different number in neutrons. Because when you add the total protons and neutrons together you get your atomic mass. So this can be written as X=said element, top number above=different atomic mass, bottom number below=atomic number. Hope this help!!
Be careful because answer A has same masses but different atomic numbers so different atoms(elements)!!!
Use the grams to moles first. The molar mass of sodium is 22.99g, so 10/22.99 ≈ 0.43 moles. The use moles to atoms conversions. 0.43 x (6.022 x 10^23), which would be about 2.62 x 10^23 atoms in 10g of sodium.
