Indicate which reactions are redox reactions. check all that apply. check all that apply. 2na(s)+cl2(g)→2nacl(s) cd(s)+pb2+(aq)→cd2+(aq)+pb(s) pb(no3)2(aq)+2licl(aq)→pbcl2(s)+2li no3(aq) c(s)+o2(g)→co2(g)

Redox reactions are those in which the oxidation numbers of the elements involved are changed.

Equation 1:

2Na(s) + Cl2(g) --> 2NaCl

The oxidation numbers of Na and Cl in the reactant side are both zero because they are in elemental form. In the product side, however, the oxidation numbers are +1 and -1, respectively. Hence, this is an example of redox reaction.

Equation 2:

Cd(s) + Pb+2(aq) --> Cd2+(aq) + Pb(s)

The oxidation numbers of Cd and Pb+2 in the reactant side are 0 and +2, respectively. They are, however, +2 and 0 in the product side. Hence, this is also a redox reaction.

Equation 3:

Pb(NO3)2(liq) + 2LiCl(aq) --> PbCl2(s) + 2LiNO3(aq)

The oxidation numbers of the involved ions (both cations and anions) are not changed. Hence, this is NOT an oxidation reaction.

Equation 4:

C(s) + O2(g) --> CO2(g)

 Just as the equation 1 and 2, the oxidation numbers of the reactants are not similar to those in the product. Hence, this is an example of oxidation reaction. 

your parents i think this could be it

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.