Chemistry, 17.02.2021 01:10 brockmorrison3468

35 POINTS An atom of an element has 54 protons. Some of the element’s atoms have 77 neutrons.

Others have 79 neutrons.

What is the mass number for the atom that has 77 neutrons?
What element is this? (Write the full name of the element.)
How many electrons does this element have?
What is its atomic number?
What is the mass number for the atom that has 79 neutrons?
What element is this? (Write the full name of the element.)
How many electrons does it have?
What is its atomic number?

Answers: 2

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Answer from: Quest

assuming that your periodic table has eighteen columns, you should highlight the four elements in the third column from the left of the table.

explanation

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the $3d$ have energy higher than those in the $4 s$ orbital while lower than those of the $4 p$ orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the $4s$ orbital is therefore filled right after $3p$ orbitals and before $3 d$ orbitals.

potassium has electron configuration $[\text{ar}] 4 s^{1}$ and calcium $[\text{ar}] 4 s^{2}$ . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration $[\text{ar}] 4 s^{2} \; 3d^{1}$ and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the $ns^{2} \; (n-1) p^{1}$ and should be highlighted as well.

Answer from: Quest

The answer is probably c. xylem

Answer from: Quest

a corroding iron, if that's one of your choices

Answer from: Quest

Electron equations of the given changes are as follow,a) cu → cu⁺² + 2e⁻b) mg⁺² + 2 e⁻ → mgc) cl⁻ → cl + 1e⁻d) s + 2 e⁻ → s²⁻e) o²⁻ → o + 2 e⁻f) p + 3 e⁻ → p³⁻g) fe²⁺ → fe³⁺ + 1 e⁻h) s²⁻ → s⁴⁺ + 6 e⁻

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35 POINTS An atom of an element has 54 protons. Some of the element’s atoms have 77 neutrons.
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