1) El hierro tiene de número atómico 26 y de número másico 55. Las partículas del átomo neutro son:a. Número de protones _______________
b. Número de electrones _______________
c. Número de neutrones _______________

Final answer:

The half-life of sodium-25, when 1.00 gram of a 16.00-gram sample remains unchanged after 237 seconds, is approximately 59.3 seconds. This solution was found by calculating the number of times the sample halved and dividing the total time by this figure.

Explanation:

The question asks for the half-life of sodium-25 if 1.00 gram of a 16.00-gram sample remains unchanged after 237 seconds. In nuclear physics and nuclear chemistry, the half-life is the amount of time it takes for half of a sample of a radioactive substance to undergo decay.

Given that sodium-25 has gone from 16 grams to 1 gram, we can see that 1/16th of the original amount is left after 237 seconds. In other words, the quantity of sodium-25 has halved approximately 4 times. Therefore, the half-life will be the total time divided by the number of half-lives.

By dividing 237 seconds by 4, we get 59.25 seconds. So, the closest accurate answer is (2) 59.3s.

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4.Solution

Further explanation

Mixtures are materials composed of two or more kinds of substances that still possess their original properties. Mixtures can also be said to represent a combination of several substances, elements or compounds

There are two types of mixtures, i.e., homogeneous mixture (or solution) and heterogeneous mixture.

• Homogeneous mixture: mixture which each part contains a similar amount of solute, for example, vinegar acid solution, sugar solution, and salt solution.
• Heterogeneous mixes: mixtures of which each part contains an unequal amount of solute, for example, river water, sewage water, and coffee drinks.

The solution is a homogeneous mixture of two or more substances that dissolve one another and each of the constituent substances cannot be distinguished physically anymore.

• The solution consists of two components, i.e., solute and solvent.
• For example, a salt solution consists of salt as a solute and water as a solvent.

In chemistry, we already know the phase of matter or state of matter, i.e., solid (s), liquid (l), gas (g), and aqueous (aq). Every chemical solution in a reaction is labeled as an aqueous phase, e.g, as a salt solution.

Consider the following examples:

• as a solid metal iron, an element.
• as liquid water.
• as ice solids.
• as water vapor with a gaseous phase.
• are compounds of the same chemical formula but different phases.

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Keywords: which must be, a mixture of substances, solid, liquid, gas, solution, homogeneous, heterogeneous, phase of matter, state, aqueous, salt, water

Answer:

E. 1.18x10^4nm/ms^2

Explanation:

The aceleration of the train is given in m/s². We need to conver, first, the meters to nm and then, the seconds to ms as follows:

11.8m/s² * (1x10⁹nm / 1m) = 1.18x10¹⁰nm / s²

Now, as 1s is equal to 1000ms:

1.18x10¹⁰nm / s² * ((1s)² / (1000ms)²)) =

1.18x10⁴nm / ms²

Thus, right option is:

E. 1.18x10^4nm/ms^2

Final answer:

A train's acceleration of 11.8 m/s^2 converts to 11.8*10^7 nm/ms^2 while converting from meters to nanometers and from seconds squared to milliseconds squared.

Explanation:

To convert a value from meters (m) to nanometers (nm), we must multiply by the conversion factor of 1×10^9nm/1m. A nanometer is one billionth (10^-9) of a meter. In this case, the train is accelerating at 11.8 m/s2. Therefore, the acceleration in terms of nanometers per second squared (nm/s2) is 11.8 * 109 nm/s2. To convert this value to nanometer per millisecond squared (nm/ms2), we know there are 1000 milliseconds (ms) in a second (s). Hence, we divided by 1000 squared, resulting in 11.8 * 109 nm/s2 divided by 10002 to get the answer in (nm/ms2). This gives us 11.8*107 nm/ms2, so the correct answer is C.

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Answer: Option (a) is the correct answer.

Explanation:

It is known that for non-metals, on moving down a group there will be decrease in electronegativity of elements.

Smaller is the size of a non-metal, more easily an electron will be attracted by its nucleus. Whereas larger is the size of element more is the number of electrons present in the atom.

Hence, more will be the number of shells and attraction between the nucleus and outermost electrons will decrease. As a result, an electron will not easily get attracted by a larger atom.

Thus we can conclude that fluorine is the element that has the greatest electronegativity.