All categories

3 years ago

An atom has a mass number of 9 and 5 neutrons. What is its atomic number? A 19 B. 14 O c.4 D. 11 SN

Chemistry

2 answers:

nika2105 [10]3 years ago

5 0

Answer:

$\boxed {\boxed {\sf C. \ 4}}$

Explanation:

First, define some important terms.

Mass number: the sum of the nucleons (protons and neutrons)
Atomic number: the number of protons

We know the mass number is 9. So, the sum of protons and neutrons is 9.

$mass \ number =9$

$protons + neutrons = 9$

We also know the atoms has 5 neutrons. Therefore, the rest must be protons.

$protons + 5 \ neutrons =9$

Subtract the 5 neutrons from the overall mass number of 9.

$protons = 9- 5 \ neutrons \\$

$protons=4$

There are 4 protons, so the atomic number is also 4. This atom is beryllium.

butalik [34]3 years ago

4 0

Answer:

C. 4

Explanation:

the mass is the number of neutrons and Protons. so if you have 5 neutrons that means the rest are Protons... and the number of Protons is the Atomic number meaning the Element number... Beryllium is the element :)

You might be interested in

10. A small gold nugget has volume of 0.87 cm3. What is its mass if the density of gold is 19.3 g/cm3?

bulgar [2K]

Answer:

16.791 grams

Explanation:

The density formula is:

$d=\frac{m}{v}$

Rearrange the formula for m, the mass. Multiply both sides of the equation by v.

$d*v=\frac{m}{v}*v$

$d*v=m$

The mass of the gold nugget can be found by multiplying the density and volume. The density is 19.3 grams per cubic centimeter and the volume is 0.87 cubic centimeters.

$d= 19.3 g/cm^3\\v-0.87 cm^3$

Substitute the values into the formula.

$m=d*v$

$m= 19.3 g/cm^3*0.87 cm^3$

Multiply. Note that the cubic centimeters, or cm³ will cancel each other out.

$m=19.3 g*0.87$

$m=16.791 g$

The mass of the gold nugget is 16.791 grams.

8 0

3 years ago

Calculate the mass of nitric acid required to make a 250mL solution with 2.40 ph

meriva

The mass of nitric acid required to make the given solution is 0.0627 g.

The given parameters:

Volume of the acid, V = 250 mL
pH of the acid, = 2.4

The hydrogen ion (H⁺) concentration of the nitric acid is calculated as follows;

$H^+ = 10^{-pH}\\\\H^+ = 10^{-2.4}\\\\H^+ = 0.00398$

The molarity of the nitric acid is calculated as follows;

$= 0.00398 \ H^+ \times \frac{1 \ M \ HNO_3}{1 \ H^+} \\\\= 0.00398 \ M$

The number of moles of the nitric acid is calculated as follows;

$moles = M\times L\\\\moles = 0.00398\ M \ \times \ \frac{250 \ mL}{1000} \\\\moles = 9.95 \times 10^{-4} \ mol.$

The molar mass of nitric acid is calculated as;

$HNO_3 = (1) \ + (14) \ + (16 \times 3) = 63 \ g/mol$

The mass of the nitric acid contained in the calculated number of moles is calculated as;

$mass = moles\ \times \ molar \ mass\\\\mass = 9.95\times 10^{-4} \ mol. \ \times \ 63 \ g/mol\\\\mass = 0.0627 \ g$

Thus, the mass of nitric acid required to make the given solution is 0.0627 g.

Learn more about molarity of acids here: brainly.com/question/13864682

3 0

2 years ago

What is the purpose of the subscripts, or small numbers, in a chemical formula?

dlinn [17]

Answer: To show the number of atoms present.

Explanation: As in CO² (Carbon dioxide), there is a small 2 next to the symbol "O" (oxygen) to explain that there are two oxygen atoms.

7 0

3 years ago

A fish is removed from a contaminated lake. You determine that a particular toxin (X) is present in its cells at concentration X

netineya [11]

The level of toxins in the fish's cell is equivalent to the level of toxins in the water. Therefore, in order to reduce the toxins further, we should replace the now contaminated water with clean water. After the level of toxins in the fish's cell stops reducing, we replace the water with clean water once again.

3 0

2 years ago

Concentrations-

Arisa [49]

Moles of HCl is 3.47mol

Work shown on photo

6 0

3 years ago

An atom has a mass number of 9 and 5 neutrons. What is its atomic number? A 19 B. 14 O c.4 D. 11 SN​

An atom has a mass number of 9 and 5 neutrons. What is its atomic number? A 19 B. 14 O c.4 D. 11 SN