Answer:
8.73
Explanation:
when you are adding or subtracting numbers, the sigfig (significant figure) is based on how many numbers after the decimal. with this info, we can see that 15.67 has 2 sigfigs and 6.943 has 3 sigfigs. when you subtract normally, you would get 8.727, which has 3 sigfigs, so you would round the last 7 up to get 8.73 with 2 sigfigs!
also it is to 2 sigfigs because we know that we go by the least number of sigfigs. hope this helped!
Answer:
in alpha decay, shown in Fig. 3-3, the nucleus emits a 4He nucleus, an alpha particle. Alpha decay occurs most often in massive nuclei that have too large a proton to neutron ratio. An alpha particle, with its two protons and two neutrons, is a very stable configuration of particles. Alpha radiation reduces the ratio of protons to neutrons in the parent nucleus, bringing it to a more stable configuration. Many nuclei more massive than lead decay by this method.
Explanation:
The valency of an atom is equal to the number of electrons in the outer shell if that number is four or less. Otherwise, the valency is equal to eight minus the number of electrons in the outer shell. Once you know the number of electrons, you can easily calculate the valency.
Answer: Helium is least likely to form bonds.
Explanation:
Helium has the electronic configuration 
. As the 1s sub-shell is completely filled so there is no need for helium to form bonds with other atoms.
Whereas, nitrogen has the electronic configuration 
. As the p sub-shell is half filled, it has the tendency to accept more electrons. Therefore, nitrogen is more susceptible to form bonds as compared to helium.
Thus, it is concluded that helium is least likely to form bonds.
