Answer : The energy of the photon emitted is, -12.1 eV
Explanation :
First we have to calculate the 
orbit of hydrogen atom.
Formula used :
where,
= energy of 
orbit
n = number of orbit
Z = atomic number of hydrogen atom = 1
Energy of n = 1 in an hydrogen atom:
Energy of n = 2 in an hydrogen atom:
Energy change transition from n = 1 to n = 3 occurs.
Let energy change be E.
The negative sign indicates that energy of the photon emitted.
Thus, the energy of the photon emitted is, -12.1 eV
Answer: Multiple covalent bonds may occur in atoms that contain carbon,nitrogen, or <u><em>oxygen</em></u>.
Answer;
-The charges of the positive and negative copper ions cancel each other out.
Explanation;
-A normal atom has a neutral charge with equal numbers of positive and negative particles.That means an atom with a neutral charge is one where the number of electrons is equal to the atomic number.
-Atoms are electrically neutral because they have equal numbers of protons (positively charged) and electrons (negatively charged). If an atom gains or loses one or more electrons, it becomes an ion. If it gains one or more electrons, it now carries a net negative charge, and is thus anionic.
Answer:
one move parallel to the direction of the movement and the other move perpendicular to towards the direction of the move of wave..transverse and longitudinal wave
