Answer: It will take 29 years for a 10.0-gram sample of strontium-90 to decay to 5.00 grams
Explanation:
Radioactive decay process is a type of process in which a less stable nuclei decomposes to a stable nuclei by releasing some radiations or particles like alpha, beta particles or gamma-radiations. The radioactive decay follows first order kinetics.
Half life is the amount of time taken by a radioactive material to decay to half of its original value.
Half life is represented by 
= rate constant
Given : Strontium-90 decreases in mass by one-half every 29 years , that is half life of Strontium-90 is 29 years.
As half life is independent of initial concentration, it will take 29 years for a 10.0-gram sample of strontium-90 to decay to 5.00 grams as the amount gets half.
C. An atom of helium has its valence electrons in its first energy level, it wouldn't and can't satisfy the Octet rule as it only has 2 electrons, but with 2, it has a full shell, as the first energy level can hold only 2 electrons.
The answer is true.
Explanation:
The balance of trade is nothing but the country's exports minus the country's imports.
Exports means, what you produce in the country and sell it to other countries, whereas imports means what you get or buy from the other countries.
When you export more than you import, you have trade surplus .In that case the income from exports are more than the money spent. So you have a trade surplus.
When you import then you have a trade deficit or your income is low. Most of the countries want a trade surplus.
But when the Income from exports and the money spent on imports are the same , the situation is that of balance of trade equilibrium, where the income from exports is equal to the money its residents pay for the imports.
The formula for hydrogen-hydrogen is H-H
Extensive property is that which depends on the amount of matter in a sample. For example: mass, volume, size are all extensive properties
Intensive properties are independent of the amount of matter. These include; boiling point, melting point, color and so on.
In the given examples:
Both sample A and B have the same volume (1000 ml) i.e. the same extensive property. However, they have different freezing points i.e. different intensive property.
Ans: D) The two substances are not the same because their intensive property is different.
