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olasank [31]
3 years ago
7

Use the helium-4 isotope to define atomic number and mass number. why does knowledge of atomic number enable us to deduce the nu

mber of electrons present in an atom
Chemistry
1 answer:
Nuetrik [128]3 years ago
8 0
Helium - 4 isotope has 2 protons and 2 neutrons.

Its atomic number is 2 (the number of protons). Atomic number is the number of protons in the atom of an element and it identifies the element. All the isotopes of an element have the same atomic number (same number of protons). So, all the isotopes of hellium have 2 protons.

The number 4 that identifies the helium - 4 isotope is the mass number, i.e. the number of protons plus the number of neutron. So, helium-4 isotope has 2 protons and 2 neutrons. While, other isotopes of helium have 2 protons but different number of neutrons.

The atomic number enable us to deduce the number of electrons in an atom because the atoms are neutral, which implies that the positive and negative charge are equal. Given that the magnitude of the charge of electons and protons are equal but the sign is opposed (protons are positve and electrons are negative) the number of electrons in the atom equals the number of protonts. That is why the atomic number is also the number of electrons of the atom.
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Magnesium has three naturally occurring isotopes with masses of 23.99 amuamu, 24.99 amuamu, and 25.98 amuamu and natural abundan
bonufazy [111]

Answer:

24.309 g/mol

Explanation:

To get the atomic mass, all we have to do is calculate with the masses of the three isotope, the real quantity present, taking account of the percent and then, do a sum of these three values. Like a pondered media.

For the first isotope:

23.99 * (78.99/100) = 18.95 g/mol

For the second isotope:

24.99 * (10/100) = 2.499 g/mol

For the last isotope:

25.98 * (11.01/100) = 2.86 g/mol

Now, let's sum all three together

AW = 18.95 + 2.499 + 2.86

AW = 24.309 g/mol

3 0
4 years ago
Read 2 more answers
Which of the following compounds contains the lead (iv) ion?
Oliga [24]
Oxidation state of Pb in PbO2 is +4.
Oxidation state of Pb in PbCl2 is +2.
Oxidation state of Pb in Pb2O is +1.
Oxidation state of Pb in Pb4O3 is +6/4.

Hence option A. PbO2 is correct.
Hope this helps, have a nice day!
6 0
3 years ago
Read 2 more answers
What does this equation, 2 C(s) + O 2(g) ® 2 CO(g), tell us?
Zanzabum

Answer:

D. All of these.

Explanation:

For an equation to be balanced the number of atoms of each kind in the reactants and the products should be the same.

Then from this equation, CO  is a product.

Last, two carbon atoms undergo reaction with the oxygen molecule for complete reaction to occur. Each atom combines with one oxygen atom.

7 0
3 years ago
Read 2 more answers
Why are nanowhiskers used to repel stains on fabrics??
WINSTONCH [101]

Nanowhiskers or cellulose nanofibers are nano-structured cellulose produced by bacteria. They have relatively high crystallinity and ability to form a dense network held together by inter-fibrillar bonds that has the tendency to act as a barrier through their film-forming properties to which they can repel stains on fabric.

 

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7 0
4 years ago
Is a bimolecular reaction necessarily second-order? Is a second-order reaction necessarily bimolecular? Answer, with explanation
Kruka [31]
A bimolecular reaction is always a second-order reaction, but a second-order reaction is not always a bimolecular reaction.

The most important thing to take note of is that molecularity of a reaction is a concept applicable to only elementary reactions, meaning non-complex. In a way, elementary reactions are basic and achieved in one step. Complex reactions involve intermediate steps before achieving the desired reaction.

Molecularity is equal to the sum of the coefficients of the reactants, so two reactants give a second-order bimolecular reaction. However, second-order reactions can involve more than two reactants especially in complex reactions.
3 0
3 years ago
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