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3 years ago

Electrons in atoms exist in particular energy level. A ___ must be emitted or absorbed to move between energy levels.

Chemistry

1 answer:

svetlana [45]3 years ago

8 0

Answer:

Photon of light

Explanation:

According to Bohr's model of the atom, electrons in atoms are found in specific energy levels. These energy levels are called stationary states, an electrons does not radiate energy when it occupies any of these stationary states.

However, an electron may absorb energy and move from one energy level or stationary state to another. The energy difference between the two energy levels must correspond to the energy of the photon of light absorbed in order to make the transition possible.

Since electrons are generally unstable in excited states, the electron quickly jumps back to ground states and emits the excess energy absorbed. The frequency or wavelength of the emitted photon can now be measured and used to characterize the transition. This is the principle behind many spectrometric and spectrophotometric methods.

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What is the mass of an original 5.60-gram sample of iron-53 that remains unchanged after 25.53 minutes?

olga_2 [115]

Answer is 0.7 g

Reason: Given: mass of Fe = 5.60 gWe know that, half life of Fe-53 = t1/2 (Fe-53) = 8.51 min.
Thus, after 25.53 mins, number of half life passed = 25.53/8.51= 3

Now, Amount left after first half life = 5.60g/2 = 2.80 g
Amount left after second half life = 2.80g/2 = 1.40 g
Amount left after third half-life = 1.40g/2 = 0.7g.

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3 years ago

Name two elements that have properties similar to those of beryllium and have average atomic masses higher than 130

sertanlavr [38]

In the periodic table, elements of the same group are characterized by having the same similar properties.
So, first we will check the elements that lie within the same group as beryllium and then we will attempt to choose the elements with atomic mass higher than 130.

So, elements in the same group as beryllium are: magnesium, calcium, strontium, barium and radium.
Among these elements, we will find that:
radium has atomic mass of 226 amu
barium has atomic mass of 137.327 amu

Based on this, the two elements would be barium and radium.

3 0

3 years ago

CO(g) + 12 O2(g) → CO2(g)The combustion of carbon monoxide is represented by the equation above.(a) Determine the value of the s

devlian [24]

Answer : The standard enthalpy change for the combustion of CO(g) is, -283 kJ/mol

Explanation :

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.

The combustion of $CO$ will be,

$CO(g)+\frac{1}{2}O_2(g)\rightarrow CO_2(g)$ $\Delta H_{rxn}=?$

The intermediate balanced chemical reaction will be,

(1) $C(s)+\frac{1}{2}O_2(g)\rightarrow CO(g)$ $\Delta H_1=-110.5kJ/mol$

(2) $C(s)+O_2(g)\rightarrow CO_2(g)$ $\Delta H_2=-393.5kJ/mol$

Now we are reversing reaction 1 and then adding both the equations, we get :

(1) $CO(g)\rightarrow C(s)+\frac{1}{2}O_2(g)$ $\Delta H_1=110.5kJ/mol$

(2) $C(s)+O_2(g)\rightarrow CO_2(g)$ $\Delta H_2=-393.5kJ/mol$

The expression for enthalpy change for the reaction will be,

$\Delta H_{rxn}=\Delta H_1+\Delta H_2$

$\Delta H_{rxn}=(110.5)+(-393.5)$

$\Delta H_{rxn}=-283kJ/mol$

Therefore, the standard enthalpy change for the combustion of CO(g) is, -283 kJ/mol

6 0

3 years ago

The following ionization energies were found for an unknown element: -

Alika [10]

Answer:

The common ion will be di-positive ion.

Explanation:

The ionization energy is defined as the amount of energy needed for removal of most loosely bound electron from an isolated atom in gaseous state.

The low ionization energy shows that the atom is able to give electron easily as after losing electron it may attain noble gas configuration or half filled stability.

Here the first and second ionization energy, both are low suggesting that the element is ready to give two electrons easily to form a di-positive ion however the third ionization energy is high which shows that it will not form tri-positive ion commonly.

7 0

3 years ago

A material has a volume of 63.0 cm3 and a mass of 28 grams. What is the density of the material in g/cm3 to the correct number

dimaraw [331]

Answer:

0.4444 g/cm³ ≅ 0.44 g/cm³ (2 significant figures).

Explanation:

Knowing that:

d = m/V,

where, d is the density of the material (g/cm³).

m is the mass of the material (m = 28 g).

V is the volume of the material (V = 63.0 cm³).

∴ d = m/V = (28 g)/(63.0 cm³) = 0.4444 g/cm³ ≅ 0.44 g/cm³ (2 significant figures).

7 0

2 years ago