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3 years ago

Give the number of protons, neutrons and electrons in 99Tc

Chemistry

1 answer:

miss Akunina [59]3 years ago

5 0

Explanation:

Tc - 99 is technetium 99.

It is a radioactive element that decays spontaneously. It has a half-life of 211,000 years and decays to stable ruthenium.

On the periodic table, it has an atomic number of 43;

Mass number = 99

Atomic number = number of protons = number of electrons in atom

Number of protons in Tc is 43

electron is 43

Mass number = number of protons + number of neutrons

Number of neutrons = mass number - number of protons = 99-43 = 56

learn more:

Atomic number brainly.com/question/2057656

#learnwithBrainly

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Determine the number of atoms in 41.0 grams of calcium, Ca. (The mass of one mole of calcium is 40.08 g.)

Dovator [93]

Hi there!

Let me know if you have questions about my answer:

6.15 × 10²⁴

Explanation:

To find the number of atoms, divide the mass of calcium (m) by its molar mass (MM). This will give you the number of moles of calcium (n).

$n = m/MM$ Start with a formula

$=\frac{41.0g}{40.08g/mol}$ Substitute values from the question

$= \frac{41.0g*1mol}{40.08g}$ Simplify

$= \frac{41.0mol}{40.08}$ Cancel out the units "g"

$= 1.022...mol$ Number of moles of calcium, with 4 significant figures

Then, multiply the number of moles of calcium (n) by Avogadro's number ( $N_{A}$ ) to find the number of calcium atoms.

$Number.of.Ca=n*N_{A}$ Start with a formula

$= 1.022mol*\frac{6.022*10^{23}Ca}{1mol}$ Substitute values from the question

$= \frac{1.022mol*6.022*10^{23}Ca}{1mol}$ Simplify

$= 1.022*(6.022*10^{23}Ca)$ Cancel out the units "mol"

$= 6.154*10^{24} Ca$ Multiply, leave one extra digit to help round. "4" tells you to round down.

$= 6.15*10^{24} Ca$ Final answer to 3 significant figures*

*When multiplying and dividing numbers, your final answer will have the same number of significant figures as the number with the least number of significant figures in the question.

40.08 has 4 significant figures. 41.0 has 3 significant figures. So, you want 3 significant figures in your final answer.

I hope this helps!

Learn more about Avogadro's number here:

brainly.com/question/1445383

Check out another answer that uses significant figures:

brainly.com/question/3721164

7 0

2 years ago

Significant digits are the number of digits that reflect the precision of a measurement or number.

Delvig [45]

Answer:

True

Explanation:

Significant digits are numbers that helps to present the precision of measurements calculations.

Numbers that do not contribute to the precision of a reading should not be counted as significant.

There are rules of assigning significant numbers:

Leading or trailing zeros are insignificant and should only be counted as a place holder.
All non-zero digits are significant
Zeroes between non-zero digits are significant.
Leading zeros in a decimal are significant before the number.
All the numbers in a scientific notation are significant.

5 0

3 years ago

The teacher shows students a pictorial model of an atom. Which element is

frutty [35]

Answer:

C. Fluorine because the model has 9 protons which is represented by the atomic number

Explanation:

We usually identify an element by the number of protons in them. The number of protons is the atomic number of an atom.

Every atom has a specific number of protons in them.
This number of protons is the atomic number.
According to the periodic law, atoms are arranged on the periodic table based on their atomic number.
The given fluorine atom has 9 protons which represents the atomic number of the atom.
This way, the given number clearly shows the right model for identifying the chemical specie.

4 0

2 years ago

What is sex and what does it do

zhenek [66]

Intercourse between two beings, usually male and female to procreate.

6 0

2 years ago

Read 2 more answers

PLEASE HELP I will mark brilleint

zhuklara [117]

1. b
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3.c
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6 0

3 years ago