A. Neutrons and electrons

Mrac [35]

Answer:

The term "sustainable communities" has various definitions, but in essence refers to communities planned, built, or modified to promote sustainable living. Sustainable communities tend to focus on environmental and economic sustainability, urban infrastructure, social equity, and municipal government.

7 0

3 years ago

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Volume can be measured in:

Anna11 [10]

Volume can be measured in cubic centimetres (which is the small 3 next to the unit and is higher)

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4 years ago

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What is the only force that acts between particles of helium gas?

Natalka [10]

Answer: The only force that acts between particles of helium gas is Vanderwaal forces.

Explanation:

When molecules are uncharged in nature but still combined together due to the dipole moment of elements then this force holding the molecules together is known as Vanderwaal forces.

This force is weak in nature.

For example, particles of helium gas has Vanderwaal force between its atoms.

Thus, we can conclude that the only force that acts between particles of helium gas is Vanderwaal forces.

8 0

3 years ago

Given the following equation: 2K + Cl2 -> 2KCl How many grams of KCl is produced from 4.00 g of K and excess Cl2?

Thepotemich [5.8K]

Answer:

42.65g

Explanation:

Given parameters:

Mass of K = 4g

Unknown: Mass of KCl

Solution:

Complete equation of the reaction:

2K + Cl₂ → 2KCl

To solve this problem, we know that the reactant in short supply is potassium K and this dictates the amount of products that would be formed. The chlorine gas is in excess and we can't use it to determine the amount of product that would form.

Now, we work from the known to the unknown. Since we know the mass of K given in the reaction, we can simply find the molar relationship between the reacting potassium and the product. We simply convert the mass to mole and compare to the product. From there we can find the mass of KCl that would be produced.

Calculating number of moles of K

Number of moles = $\frac{mass}{molar mass}$

Number of moles of K = $\frac{4}{39}$ = 0.103mol

From the given reaction equation:

2 moles of K will produce 2 moles of KCl

Therefore 0.103mol of K will produce 0.103mol of KCl

To find the mass of KCl produced,

Mass of KCl = number of moles of KCl x molar mass

Molar mass of KCl = 39 + 35.5 = 74.5gmol⁻¹

Mass of KCl = 0.103 x 74.5 = 42.65g

4 0

3 years ago

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Explain in detail what information can be learn about atoms of different elements by examining the periodic table. For the maxim

pav-90 [236]

Answer:

See below this long answer.

Explanation:

These are the main features of the periodic table that you will be able to relate with some property trends of the atoms like size, energy levels, valence electrons, electronegativity, and ionization energy.

A) Features:

1. Elements are arranged in increasing order of atomic number, i.e. number or protons.

2. Since atoms are neutrals, the number of electrons equals the number of protons, and, as result, the elements are arranged in increasing order of number of electrons.

3. The elements are arranged in 18 columns and 7 rows.

4. The rows are named period and correspond to the principal energy level (n): first row corresponds to n = 1, second row corresponds to n = 2, third to n = 3, and so on up to n = 7. The number of elements in each period are:

Period 1, n = 1, 2 elements

Period 2, n = 2, 8 elements

Period 3, n = 3, 8 elements

Period 4, n = 4, 18 elements

Period 5, n = 5, 18 elements

Period 6, n = 6, 32 elements (this includes the 14 lanthanides)

Period 6, n = 7, 32 elements (this includes the 14 lanthanides)

That makes a total of 118 elements.

5. The columns are named groups and they indicate the number of valence electrons

Group 1: 1 valence electron

Group 2: 2 valence electrons

Group 13: 3 valence electrons

Group 14: 4 valence electrons

Group 15: 5 valence electrons

Group 16: 6 valence electrons

Group 17: 7 valence electrons

Group 18: 8 valence electrons

Groups 3 through 12 includ the transition metals and due they have subshells that are not completely filled, their valence electrons vary.

More like a reference than as a rule these are the number of valence electrons for these groups.

Group 3: 3 valence electrons

Group 4: 2-4 valence electrons

Group 5: 2-5 valence electrons

Group 6: 2-6 valence electrons

Group 7: 2-7 valence electrons

Group 8: 2-3 valence electrons

Group 9: 2-3 valence electrons

Group 10: 2-3 valence electrons

Group 11: 1-2 valence electrons

Group 12: 2 valence electrons

B) Property trends

1. Atomic radius (size)

Down a period (from left to right): due to the increase of the positive charge (number of protons) while the main energy level (n) does not change, the electrons in the valence shell feel a stronger atraction to the nucleus causing that the atomic radius decrease from left to right.

Down a group (top to bottom): due to the increase of the main energy level, the outermost orbital is bigger and the atoms become bigger. Thus the trend is that the atomic radius increase when you go down a group.

2. First ionization energy

Down a period (from left to right): due to the increase of the nuclear charge (such as explained above) the greater attractive force makes that, in general, the first ionization energy increase from left to right.

Down a group (top to bottom): due to the increase in the size of the atom, , generally, the energy to remove an electron from the outermost shell, decrease.

3. Electronegativity

This is the relative ability to atract electrons in a covalent bond. It increases from left to right and from bottom to top: the most electronegative atoms is fluor.

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4 years ago