What is the oxidation half-reaction for mg(s) + zncl2(aq) mgcl2(aq) + zn(s)?

a. zn(s) --> zn^2+ + 2e-
b. mg(s) --> mg2+ + 2e-
c. zn^2+ + 2e- --> zn(s)
d. mg^2+ + 2e- --> mg(s)

B)

Explanation: Oxidation is loss of electrons and reduction is gain of electrons. When an element or ion loses electrons then its positive charge increases and when it gains electrons then charge decreases.

In the given equation, on reactant side Mg has zero charge and Zn has +2 charge. On product side, Mg has +2 charge and Zn has zero charge.

Since the charge of Mg is increasing from zero to +2, its oxidation.

We can ignore choice A and C since none of these have Mg. Choice D could also be ignored as it shows reduction of Mg as its changing from +2 to 0 state.

Hence, the correct choice is B as it shows an oxidation of Mg.

B)

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.