The electron affinity of an element is positive if energy is absorbed during the process of accepting an electron and negative if energy is released during the process. Using the electron configuration of the atom or ion undergoing the addition of an electron, predict whether the electron affinity will be positive or negative for the following reactions, and classify them accordingly. Atom or ion Electron configuration
Ne 1s22s22p6
Br 1s22s22p63s23p64s23d104p5
Na 1s22s22p63s1
Mg 1s22s22p63s2
Cl 1s22s22p63s23p6

See explanation

Explanation:

Ne is a noble gas. It already has an octet of electrons hence, the electron affinity of neon is negative.

Br is a halogen, halogens need one electron to complete their octet. The electron affinity for bromine is negative.

Sodium is a metal that has only one electron in its outermost shell. The electron affinity of sodium is positive.

Magnesium is a metal having two electrons in its outermost shell. The electron affinity of magnesium is positive.

Chlorine is another halogen, energy is released when an electron is added to chlorine hence the electron affinity of chlorine is negative.

explanation:

metals have excess of electrons whereas non-metals have deficiency of electrons. thus, in order to gain stability metals easily donate their electrons to the non-metals.

for example, electronic configuration of sodium is and electronic configuration of phosphorous is .

when a phosphorous atom and sodium atom combine together then sodium will donate is extra one electron to the phosphorous atom. as a result there will be formation of ionic bond between sodium and phosphorous.

the reaction will be as follows.

there, are three sodium sodium atoms and each of them will donate its one extra electron to phosphorous atom. thus, the sub-shell of phosphorous gets completely filled.  

thus, we can conclude that electrons are transferred from atoms of sodium to atoms of phosphorous. this transfer makes the sodium atoms donate one electron and the phosphorous atoms to gain one electron. as a result, the sodium and phosphorus atoms strongly attract each other.

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"