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Lunna [17]
3 years ago
8

212 pb 82 is the isotope notation for iron. what is the atomic number, mass number, and number of both protons and neutrons?

Chemistry
1 answer:
o-na [289]3 years ago
5 0

Hello!

The mass number in isotope notation is denoted A, the atomic number is denoted as Z, and the element is denoted as X.

In the given isotope, the mass of the isotope is 212 amu, and the atomic number is 82.

We know that the number of electrons, and protons are equal to the atomic number. Therefore, there are 82 protons. Also, to find the number of neutrons, we subtract the atomic number from the atomic mass.

212 - 82 = 130 neutrons

<u>Final answers</u>:  

  1. Atomic Number: 82
  2. Mass number: 212
  3. Number of Protons: 82
  4. Number of Neutrons: 130
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Rank the following elements by electron affinity, from most positive to most negative EA value. Rank from most positive to most
Svetlanka [38]

Answer:

Most positive = rubidium

Most negative = fluorine

Explanation:

Electron affinity of an element is the energy released when an electron is attached to a neural atom to form an ion in its gaseous state.

X + e⁻ → X⁻

Electron affinity is similar to electronegativity which is the tendency at which an atom accepts an ion towards itself.

Electron affinity increases across the period and decreases down the group in the periodic table.

In the above option,

Fluorine has the highest electron affinity

Rubidium has the lowest electron affinity

Tellurium and then finally Phosphorus

Helium in this case would have the lowest electron affinity because it has filled orbital and does not require any electron to attain stability. Technically, Helium has the lowest or is expected to have the lowest electron affinity which is close to zero according to quantum mechanics.

Most positive = rubidium

Most negative = fluorine.

You can check periodic table for their exact values

6 0
3 years ago
Pentaborane-9, B5H9, is a colorless, highly reactive liquid that will burst into flame when exposed to oxygen. The reaction is 2
mina [271]

<u>Answer:</u> The amount of energy released per gram of B_5H_9 is -71.92 kJ

<u>Explanation:</u>

For the given chemical reaction:

2B_5H_9(l)+12O_2(g)\rightarrow 5B_2O_3(s)+9H_2O(l)

The equation used to calculate enthalpy change is of a reaction is:  

\Delta H^o_{rxn}=\sum [n\times \Delta H^o_f_{(product)}]-\sum [n\times \Delta H^o_f_{(reactant)}]

The equation for the enthalpy change of the above reaction is:

\Delta H^o_{rxn}=[(5\times \Delta H^o_f_{(B_2O_3(s))})+(9\times \Delta H^o_f_{(H_2O(l))})]-[(2\times \Delta H^o_f_{(B_5H_9(l))})+(12\times \Delta H^o_f_{(O_2(g))})]

Taking the standard enthalpy of formation:

\Delta H^o_f_{(B_2O_3(s))}=-1271.94kJ/mol\\\Delta H^o_f_{(H_2O(l))}=-285.83kJ/mol\\\Delta H^o_f_{(B_5H_9(l))}=73.2kJ/mol\\\Delta H^o_f_{(O_2(g))}=0kJ/mol

Putting values in above equation, we get:

\Delta H^o_{rxn}=[(5\times (1271.94))+(9\times (-285.83))]-[(2\times (73.2))+(12\times (0))]\\\\\Delta H^o_{rxn}=-9078.57kJ

We know that:

Molar mass of pentaborane -9 = 63.12 g/mol

By Stoichiometry of the reaction:

If 2 moles of B_5H_9 produces -9078.57 kJ of energy.

Or,

If (2\times 63.12)g of B_5H_9 produces -9078.57 kJ of energy

Then, 1 gram of B_5H_9 will produce = \frac{-9078.57kJ}{(2\times 63.12)}\times 1g=-71.92kJ of energy.

Hence, the amount of energy released per gram of B_5H_9 is -71.92 kJ

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3 years ago
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frez [133]

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Explanation: Hope that helps :)

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3 years ago
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Aleks [24]

Answer:

Increase is the answer

Explanation:

Increase is the answer hopes this helps you

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Answer

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Explanation:

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