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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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A doorknob makes it easier for you to open doors because it is what type of simple machine?
vagabundo [1.1K]

Answer: Wheel and Axle

Both of these work together to form a simple machine. You can't have one without the other.

If you try to turn just the axle itself, then you'll find it takes a lot of work. This is because the inertia of the axle wants to keep the object at rest. Also, you won't have a lot of torque due to the small radius compared to what a doorknob can offer.

Using a doorknob is like putting a (steering) wheel on an axle. This increases the radius and therefore increases the torque. You put in less work into the system and get more out of it.

5 0
3 years ago
How many joules would be absorbed for the water in Problem 1
9966 [12]

Answer:

5000 cal X 4.184 J/cal =

Explanation:

20,920 jules

8 0
3 years ago
Which elements are present in the compound aluminium nitrate?
PSYCHO15rus [73]

Answer:

Aluminum nitrate is a salt composed of aluminum and nitric acid, belonging to a group of reactive chemicals - organic nitrate and nitrite compounds. The nitrate ion is polyatomic, meaning it is composed of two or more ions that are covalently bonded. This ion makes up the conjugate base of nitric acid.

Explanation:

4 0
2 years ago
Read 2 more answers
Question 9 of 10
aksik [14]

Answer:

The answer is B an open system allows energy and mass to move in and out of it

Hope it helps

7 0
2 years ago
a researcher obtains a sample of 0.070 M nitrate solition. A 20.0 mL aliquote of the nitrate solution is added to 10.0 mL of amm
katovenus [111]

Answer:

Concentration of nitrate in the new solution = 0.007 M

Explanation:

Given:

Concentration nitrate solution = 0.070 m

Volume of aliquote of the nitrate solution is add = 10.0 ml

Total volume = 100 ml

Find:

Concentration of nitrate in the new solution

Computation:

Number of M. mole = 0.070 m x 10.0 ml

Number of M. mole = 0.7 m-moles

Concentration of nitrate in the new solution = 0.7 m-moles / 100 ml

Concentration of nitrate in the new solution = 0.007 M

6 0
2 years ago
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