Assume trilobites went extinct 248 million years ago.
If a trilobite is found in a rock layer, what do you
know about the age of that rock layer?

Answer(s):

Atomic model

Bohr's greatest contribution to modern physics was the atomic model. The Bohr model shows the atom as a small, positively charged nucleus surrounded by orbiting electrons.  

Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element.

The chemical element bohrium (Bh), No. 107 on the periodic table of elements, is named for him.

Liquid droplet theory

Bohr's theoretical work contributed significantly to scientists' understanding of nuclear fission. According to his liquid droplet theory, a liquid drop provides an accurate representation of an atom's nucleus.

This theory was instrumental in the first attempts to split uranium atoms in the 1930s, an important step in the development of the atomic bomb.

Despite his contributions to the U.S. Atomic Energy Project during World War II, Bohr was an outspoken advocate for the peaceful application of atomic physics.

Quantum theory

Bohr's concept of complementarity, which he wrote about in a number of essays between 1933 and 1962, states that an electron can be viewed in two ways, either as a particle or as a wave, but never both at the same time.

This concept, which forms the basis of early quantum theory, also explains that regardless of how one views an electron, all understanding of its properties must be rooted in empirical measurement. Bohr's theory stresses the point that an experiment's results are deeply affected by the measurement tools used to carry them out.

Bohr's contributions to the study of quantum mechanics are forever memorialized at the Institute for Theoretical Physics at Copenhagen University, which he helped found in 1920 and headed until his death in 1962. It has since been renamed the Niels Bohr Institute in his honor.

Explanation:

Niels Bohr was one of the foremost scientists of modern physics, best known for his substantial contributions to quantum theory and his Nobel Prize-winning research on the structure of atoms.

Born in Copenhagen in 1885 to well-educated parents, Bohr became interested in physics at a young age. He studied the subject throughout his undergraduate and graduate years and earned a doctorate in physics in 1911 from Copenhagen University.

While still a student, Bohr won a contest put on by the Academy of Sciences in Copenhagen for his investigation into the measurements of liquid surface tension using oscillating fluid jets. Working in the laboratory of his father (a renowned physiologist), Bohr conducted several experiments and even made his own glass test tubes.  

Bohr went above and beyond the current theory of liquid surface tension by taking into account the viscosity of the water as well as incorporating finite amplitudes rather than infinitesimal ones. He submitted his essay at the last minute, winning first place and a gold medal. He improved upon these ideas and sent them to the Royal Society in London, who published them in the journal Philosophical Transactions of the Royal Society in 1908, according to Nobelprize.org.  

His subsequent work became increasingly theoretical. It was while conducting research for his doctoral thesis on the electron theory of metals that Bohr first came across Max Planck's early quantum theory, which described energy as tiny particles, or quanta.

In 1912, Bohr was working for the Nobel laureate J.J. Thompson in England when he was introduced to Ernest Rutherford, whose discovery of the nucleus and development of an atomic model had earned him a Nobel Prize in chemistry in 1908. Under Rutherford's tutelage, Bohr began studying the properties of atoms.

Bohr held a lectureship in physics at Copenhagen University from 1913 to 1914 and went on to hold a similar position at Victoria University in Manchester from 1914 to 1916. He went back to Copenhagen University in 1916 to become a professor of theoretical physics. In 1920, he was appointed the head of the Institute for Theoretical Physics.

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Answer:

Cu, Ag, Au, Rg

Explanation:

The periodic table is an arrangement of elements in rows and columns. The elements with  outer electron configuration of ms1 nd10 are Cu, Ag, Au, Rg.

The periodic table is an arrangement of elements in rows and columns. The rows are called periods while the columns are called groups.

Now we know that the group that is referred to here has an outer electron configuration of ms1 nd10. This corresponds to the elements Cu, Ag, Au, Rg.

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Answer:  123×10−7m.

Explanation:

Answer:

731.5j.

Explanation:

Basic Formula : Q = mcT.

Q - Heat gained or lost.

m - mass of the given substance.

c - specific heat capacity.

T - Change in temperature ( it often has a delta(triangle) before it.

so now we are directly asked to find the heat.

Q = mcT

m= 5g

c = 4.18

but T = 35k which means 35 kelvin.

why? because you will need to convert the two given initial and final temperatures inorder to cancel the unit kelvin out from the formula above. the target is simply to make the unit J - joule be left alone.

now We convert celsius temperature to kelvin by adding a constant of 273.15 approximately 273.

therefore - Tk = Tc + 273

which will be equivalent to 295k for the initial temperature and 330k for the final.

now granted...keep in mind to use the CHANGE in temperature which is the difference of the 2 kelvin temperatures we just converted

so T = 330k - 295k = 35k

then just substitute everything in the very 1st formula i stated above.

Q = mcT = 5 x 4.18 x 35 = 731.5 J

peace to you.

After beginning the experiment with a saturated solution, then increasing the heat, we will be left with an unsaturated solution.

To obtain the saturated solution, we must dissolve sugar in the water. We can say that the solution has become saturated when the solution is no longer able to dissolve more sugar. It has reached its capacity for the solute that it can dissolve in these conditions.

However, the temperature of a solution has an effect on the dissolving limit of the solution. That is, when a solution is heated it becomes able to dissolve more solute. Therefore, if we were to heat a saturated solution, it will be able to dissolve more solute and therefore will no longer be at its limit, meaning it is no longer a saturated solution. It has become unsaturated.

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Answer:

macromolecules

Explanation:

Polymer is composed of molecules called macromolecules that have multiple of simpler chemical units called monomers.

Answer: Particle F is an anion, and particle E is a cation

Explanation:

A particle is a cation if it has more protons  than  electrons.

A particle is an anion if it has more electrons than protons.

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Answer:

The ovary contains ovules

Explanation:

Element “X” belongs to family 2A, meaning it is part of the family that includes elements such as Be and Mg. These elements will all have 2 valence electrons and can be represented by the following Lewis diagram:

Element “Y” belongs to family 5A, meaning it is part of the family of elements that includes elements such as N and P. These elements will all have 5 valence electrons and can be represented by the following Lewis diagram:

Atoms from these two families will usually react with each other by losing or gaining valence electrons to create stable ions (an ion is what we call an atom/particle that has a charge). These stable ions form by the atoms either losing or gaining electrons until they have the same number of valence electrons as the nearest Noble Gas. This means that each ion will have a full valence shell (usually consisting of 8 electrons), often referred to as a “stable octet”, and this process of creating stable ions is often called the “octet rule”.

Atoms with fewer that 4 valence electrons will normally have a weak hold on their valence electrons and will tend to lose their valence electrons when forming ions.

Atoms with 4 or more valence electrons will normally have a strong hold on their valence electrons and will tend to gain electrons when forming ions.

The charge on the ion arises from the fact that, initially, the atom is electrically neutral because it has the same number of electrons (negative charges) as protons (positive charges). By losing electrons, the atom will end up with more protons (positive charges) than electrons (negative charges) and will form an ion with an overall positive charge. By gaining electrons, the atom will end up with more negative electrons than positive protons becoming an ion with an overall negative charge.

So, an atom of element “X”, with only 2 valence electrons, must lose its 2 valence electrons (which will be gained by element “Y”) to form a stable ion with a 2+ charge (losing two electrons leaves the ion with 2 more positive charges (protons) than negative charges, so a net charge of 2+).

An atom of element “Y”, with 5 valence electrons, must gain 3 electrons (from element “X”) to form a stable ion with a 3- charge (gains 3 extra negative charges).

We can show this process using Lewis diagrams:

From this set of diagrams you can see that in order to create stable ions of both “X” and “Y” we need these atoms to react with each other in a 3:2 ratio (we need 3 atoms of X for every 2 atoms of Y). This means that the resulting chemical formula of the compound will be:

Now, we will look at a short cut that can help you figure this out without having to draw Lewis diagrams.

Compounds are electrically neutral, meaning they must contain equal numbers of positive and negative charges. For compounds consisting of oppositely charged ions, this means that the total charge of the negative ions must be equal to the total charge of the positive ions. In other words the ions must combine in a ratio that makes their charges add to zero.

If we look at the compound we just made, X3Y2, we can confirm this:

So, now you can you predict the formula of simple ionic compounds:

from the family of elements, determine the number of valence electrons each element has

determine the charge of the ions that each atom will form using the octet rule (or look on the periodic table, most will tell you the stable ionic charges that each element can form)

determine the ratio of positive ions to negative ions that results in an overall charge of zero

Example,

What is the formula of a compound produced when an element from family 3A combines with an element from family 7A?

Answer:

Ionic Bonds

Explanation:

Ionic bonds usually occur between metal and nonmetal ions. For example, sodium (Na), a metal, and chloride (Cl), a nonmetal, form an ionic bond to make NaCl.

Answer:

0.143kg/m^3

Explanation:

density= mass / volume

Answer:

1/7 kg/cubic metres

Explanation:

Here, Density=mass /volume

=6/42

=1/7 kg/cubic metres.

Answer:

members shall perform their duties with integrity, intelligence and competence in the application of specialized skill and technical knowledge with excellence and expertise.

Explanation:

any members on duty should be wiling and ready to help at all times

Answer:

2.93×10^23

Explanation:

molecular formula of NaCl is 58.5

58.5gof NaCl=6.023×10^23

28.5g of NaCl= 6.023×10^23÷58.5×28.5

= 2.93×10^23

Answer:

It is called absolute humidity.

Explanation:

Answer:

%Li-6 = 5.996% & %Li-7 = 94.004%

Explanation:

let X₁ = Li-6 & X₂ = Li-7 where Xₙ = mole fraction

X₁ + X₂ = 1 => X₁ = 1 - X₂

6·X₁ + 7·X₂ = 6.94004

=> 6(1 - X₂) + 7·X₂ = 6.94004

=> 6 - 6·X₂ + 7·X₂ = 6.94004

=> 6 + X₂ = 6.94004

X₂ = 6.94004 - 6 = 0.94004 => %X₂ = %Li-7 = 94.004%

X₁ = 1.00000 - 0.94004 = 0.05996 => %X₁ = %Li-6 = 5.996%

A species acts as an oxidizing agent if it gains electrons in a half-reaction. Conversely, it could potentially act as a reducing agent if it loses electrons in a half-reaction.

REDOX REACTION:

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Answer:

Removing heat causes water (a liquid) to freeze to form ice (a solid). When water changes to a solid or a gas, we say it changes to a different state of matter. ... This causes the hydrogen atoms in one water molecule to be attracted to the oxygen atom in another water molecule.

Explanation:

Answer:

atomic watch

Explanation:

it is used for the measurement of time.

Answer:

Melted ionic compounds

Explanation:

This is because the ions have dissociated and for electricity to pass through a substance it is important that the substance must have ions present in it.

Answer:

element

Explanation:

hope this helps

Explanation:

Elements are pure substances that cannot be broken down into simpler substances by ordinary chemical means.

Methane is found under the ground or under marine sediments  as natural gas which is mined along with crude oil.

Methane is an alkane and has the formula CH4. It is most commonly used as fuel. Methane is the gas that has been renowned as being responsible for explosion in coal mines.

Methane is found under the ground as natural gas which is mined along with crude oil. Large deposit of natural gas is found in many countries in Asia, Africa and the middle east.

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Answer:

A force between an object and the surface it's moving over.

Explanation:

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Answer: The four forces acting on an aircraft in straight-and-level, unaccelerated flight are thrust, drag, lift, and weight.

Explanation:

Answer:

a table is a grid of rows and columns that intersect to form cells

Explanation:

Answer:

magnesium oxide

Explanation: