The valency of sodium metal

Answer:

B

Explanation:

Mass number  = number of neutrons + number of protons

Atomic number is the number of protons in the nucleus.  

58Ni   : 58 is the number of neutrons + number of protons

atomic number of Ni is 28.  Thus,  58 -28 = 30 neutrons

57Co ;  57 is the number of neutrons + number of protons

number of Co is 27. Thus, 57 – 27  = 30 neutrons

Answer:

Here is the meaning of covalent bond: covalent bond: a chemical bond in which two atoms share some of their valence electrons which creates a force that holds the atoms together

Hope this helps

Sky

A chemical bond in which two atoms share some of their valence electrons creates a force that holds the atoms together.

A covalent bond consists of the mutual sharing of one or more pairs of electrons between two atoms.

Covalent bonds have high bond dissociation energy as compared to the ionic bond. The overlapping of molecular orbital is bigger in the case of the covalent bonds as compared with ionic bonds.

Hence, covalent bonds are difficult to break and stronger than ionic bonds.

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Answer: Christy won Molly by 12cm

Explanation:

Ist step

Molly's ;ong jump was 118.3cm

Christy long jump was 51.18inches

2nd Step

we change christy score to cm so we can compare

1 inch = 2.54cm.

therefore 51.18 inches = 51.18 x 2.54= 129.9972cm

Christy won molly by 129.9971cm-118.3cm=11.69 rounded to 12cm

Christy won Molly by 12cm

Answer:

genetics

hope this helps :)

Explanation:

Answer:

c

Explanation:

Answer:

A. a best guess explanation

Explanation:

A scientific theory explains why something behaves the way it does and is usually backed up by different sources. They are not speculations and can be proven. Those which are speculations and are not proven are called hypothesis. A scientific theory can also be replaced, if it is found that it does not produce valid results, or if a better theory is proposed which is made of one or more old theories.

The historical order of atomic models from the earliest to the most recent is as: Hard sphere model, electron shell model, and wave mechanical model. Therefore, option (A) is correct.

The atomic model can be described as the model used to describe the structure and composition of the atom. The atom as a primary component of matter has been under extensive study to understand the universe.

In the classical model of an atom, the atom is made of smaller particles with an electrical charge called electrons, protons, and neutrons. To understand the atomic models, it is important to understand how these particles make up the atom.

There are five principal atomic models that have been proposed over time,  which are Dalton’s atomic model, Thomson’s atomic model, Rutherford’s atomic model, Bohr’s atomic model, and the quantum atomic model.

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Your question was incomple, most probably the complete question was,

Which group of atomic models is listed in historical order from the earliest to the most recent?

A)  Hard sphere model, electron shell model, and wave mechanical model

B)  Hard sphere model,  wave mechanical model, and electron shell model

C) Electron shell model, Hard sphere model, and wave mechanical model

D) Electron shell model, wave mechanical model, and  Hard sphere model

Answer:

Distance is a scalar quantity that refers to "how much ground an object has covered" during its motion. Displacement is a vector quantity that refers to "how far out of place an object is"; it is the object's overall change in position.

Explanation:

Answer:

D all above yes I think it's all above

Answer:  D

Explanation: All of the above.

Plz mark brainliest:)

Answer:

3.065 x 10^-24

Explanation:

hope this helps

Answer: Ionic

Explanation:

Answer:

ionic

Explanation:

Answer:

option 1

Explanation:

Forecasters, able to make more accurate predictions about the weather when using electronic tools because a wide variety of devices can be used to collect weather data from many places. Therefore, option A is correct.

Forecaster behavior is examined by forecasters to see how social, cultural, ethical, and environmental trends will likely impact it. They can determine what goods and services people will be wanting to purchase through this approach.

A person who informs you about the anticipated state of a situation: an analyst of the economy. a forecaster of weather. The term "meteorologist" has now become widely used to refer to someone who forecasts the weather and investigates objects that fall from the sky.

Fitzroy developed charts to allow forecasts to be made, which he called "forecasting the weather," and therefore created the word "weather forecast," after a storm in October 1859 that resulted in the loss of the Royal Charter.

Thus, option A is correct.

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Answer:

Breaks down rocks.

Explanation:

Weathering is the breaking down of rocks often with water. For example a sea shell will get batered with water and over time form sand.

Answer:

usage of trills and vibrato

Explanation:

earlier music used trills while later styles would use vibrato.

NO can't  be used to fill a balloon

Conditions at T 0 ° C and P 1 atm are stated by STP (Standard Temperature and Pressure). At STP, Vm is 22.4 liters/mol.

Answer options that need to be added :

a. Ne

b. NO

c. NH₃

d. CH₄

e. HF

will float in air ⇒ element or compound to fill the balloon, its density must be less than < 1.285 g/L

We can use the ideal gas formula ta find density :

[tex]\tt \rho=\dfrac{P.MW}{RT}[/tex]

Because at STP, then the constant value is

[tex]\tt \rho=\dfrac{1~atm\times MW}{0.08205\times 273.15~K}\\\\\rho=0.0446\times MW[/tex]

So that the density is determined from the MW(molecular weight) of each element or compound

Ar = 20.1797 g/mol

[tex]\tt \rho=0.0446\times 20.1797=0.9~g/L[/tex]

MW=30.006 g/mol

[tex]\tt \rho=0.0446\times 30.006=\boxed{\bold{1.338~g/L}}[/tex]

MW=17.0306 g/mol

[tex]\tt \rho=0.0446\times 17.0306=0.760~g/L[/tex]

MW=16.04 g/mol

[tex]\tt \rho=0.0446\times 16.04=0.715~g/L[/tex]

MW=20.01 g/mol

[tex]\tt \rho=0.0446\times 20.01=0.892~g/L[/tex]

Answer:

Gravity causes tides

Explanation:

(Please try to answer my most recent question!!!!!)

Answer:

7. 4H₂O

Elements: Hydrogen, Oxygen

Number of molecules: 4

Number of elements: 8 H, 4 O

Number of Atoms: 12

Explanation:

The elements are determined by the their symbol i.e. H = hydrogen.

The number of molecules is determined by the coefficient ( the number in front of everything, in this case 4).

The number of elements is determined by the coefficient and the subscripts. Multiply the coefficient by the subscript after each element. When there is no subscript, it is equal to 1.  4H₂ = 4x2 = 8;  4O = 4x1 = 4.

The number of atoms is all the individual elements added together. 8+4 = 12.

4.94 x c . (Tm-23.6)=C.(23-6-21.9)+123.13 x c. (23.6-21.9)

The law of conservation of energy can be applied to heat changes, ie the heat received/absorbed is the same as the heat released  

Q in = Q out  

Heat can be calculated using the formula:  

Q = mc∆T  

A calorimeter is a device used to measure the specific heat of material  

A metal is put into a calorimeter that contains water and there will be heat transfer:  

[tex]\tt \displaystyle m_mc_m (T_m-T)=m_wc_w(T-Tw)[/tex]

m = metal  

w = water  

T = the final temperature of the mixture  

mass of metal =(Nickel) = 4.94 g

mass of calorimeter = 12.5 g

mass of water = 123.13 g (135.63 - 12.5)

The equation

Q released (metal) = Q absorbed(calorimeter+water)

The equation :

4.94 x c . (Tm-23.6)=C.(23-6-21.9)+123.13 x c. (23.6-21.9)

Answer:

x = 3 and y= 2

Explanation:

Given equations:

           8x - 3y  = 18  - ---- (I)

           5x + 6y = 27 -------(II)

Solve this problem by elimination;

  In the elimination method, we simply find a common term that can make one of the variables in the two equation the same. Then we either add or subtract to remove the variable.

 Mulitply equation (i) by 5 to give equation III

 Mulitply equation (II) by 8 to give equation IV

     5(8x - 3y) = 5(18) ------- III

     8(5x + 6y) = 8(27) ------- IV

   40x - 15y = 90------- III

   40x + 48y = 216  ------- IV

Subtract  equation III and IV;

        -15y - 48y = 90 - 216

         - 63y = -126

                y = 2

Solve for x;

      40x - 15y = 90;

       40x - 15(2) = 90

         40x - 30 = 90

           40x = 90 + 30

              40x = 120

                 x = 3

Answer:

46.943 million km

Explanation:

From an average distance of 36 million miles (58 million kilometers), Mercury is 0.4 astronomical units away from the Sun.

From an average distance of 36 million miles (58 million kilometres), Mercury is 0.4 astronomical units away from the Sun.

(I hope this helped ^^)

Answer:

Bears and Whales

Explanation:

Bears keep themselves warm via a thick fur coat

Whales keep themselves warm with a thick layer of blubber

Answer:

letter b not c

Explanation:

next time please take a picture lucky i already took this

Answer:

I think carbon.

Explanation:

............

Answer:

Key Points

Viral replication involves six steps: attachment, penetration, uncoating, replication, assembly, and release.

During attachment and penetration, the virus attaches itself to a host cell and injects its genetic material into it.

Answer:

2.35mL

Explanation:

The amount of space a substance holds is its volume.

Density = mass (g) /volume (L)

Where;

mole = mass/molar mass

Since 1 mol of Cu contains 6.022 × 10^22 atoms.

There are 2 x 10^22/6.022 × 10^22 moles in 2 x 10^22 atoms of copper

2 x 10^22/6.022 × 10^22

2/6.022 × 10^(22-22)

0.332 × 10^0

0.332mol

Mole = mass/molar mass

0.332 = mass/63.5

mass = 63.5 × 0.332

mass = 21.08g

Density = mass/volume

Density of copper (Cu) is 8.96 g/cm³

8.96 = 21.08/v

V = 21.08/8.96

V = 2.35mL or cm³