Explanation:
Calcium is the element that has 2 valence electrons.
Half-life is the length of time it takes for half of the radioactive atoms of a specific radionuclide to decay. A good rule of thumb is that, after seven half-lives, you will have less than one percent of the original amount of radiation.
<h3>What do you mean by half-life?</h3>
half-life, in radioactivity, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay (change spontaneously into other nuclear species by emitting particles and energy), or, equivalently, the time interval required for the number of disintegrations per second of a radioactive.
<h3>What affects the half-life of an isotope?</h3>
Since the chemical bonding between atoms involves the deformation of atomic electron wavefunctions, the radioactive half-life of an atom can depend on how it is bonded to other atoms. Simply by changing the neighboring atoms that are bonded to a radioactive isotope, we can change its half-life.
Learn more about half life of an isotope here:
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brainly.com/question/13979590</h3><h3 /><h3>#SPJ4</h3>
Answer:
The symbol of the ion is A^-
Explanation:
Let A be the symbol of the element.
Proton = 17
Electron = 18
Neutron = 20
Since the element has more electrons than protons, it means it has gain electrons.
From the question given,
The difference between the electron and proton = 18 — 17 = 1
So, the element has gain 1 electron.
Therefore the symbol of the ion is A^-
Answer: Rate of decomposition of acetaldehyde in a solution is 
Explanation:
Rate law says that rate of a reaction is directly proportional to the concentration of the reactants each raised to a stoichiometric coefficient determined experimentally called as order.
For a reaction : 
![Rate=k[A]^x](https://tex.z-dn.net/?f=Rate%3Dk%5BA%5D%5Ex)
k= rate constant
x = order of the reaction = 2


Thus rate of decomposition of acetaldehyde in a solution is
Answer:
Answer in explanation
Explanation:
A. This is wrong. The reactants are on the left side of the yields arrow
B. This is wrong. They can only be at one side at a time. They cannot be on both sides at the same time.
C. The products are on the right side of the yields arrow and not at the left side
D. This is correct. The reactants are on the left side of the yields arrow.
E. This is correct. We can have varying numbers of the number of atoms on both side of the yields arrow. The numbers may differ until we decide to balance the equation