Answer:
5
Explanation:
NH4OH
The subscript gives the info that there are 4 hydrogen atoms but there is another H in the formula so you add them up.
Answer:
- <em><u>Mendeleev produced the first orderly arrangement of known elements.</u></em>
- <em><u>Mendeleev used patterns to predict undiscovered elements.</u></em>
Explanation:
- <u>Mendeleev produced the first orderly arrangement of known elements and used patterns to predict the undiscovered elements.</u>
Those two statments are true.
For the time being there were some 62 known elements. Before Medeleev some schemes to order part of the elements were proposed, but Medeleev showed the relationship between the atomic mass and the properties of the elements (supports second choice). This arrangement is known as the periodic table.
More importantly, Mendeleev predicted correctly the existance and properties of unknown elements, which is his major contribution: he left blanket spaces which where gradually filled when new elements where discovered (this supports the fourth choice).
The first modern chemistry book was written by Antoine Lavoisier (this discards first option).
Mendeleev ordered the elements by increasing mass number (this discards third choice), which was corrected later by the scientist Henry Moseley, who ordered the elements by increasing atomic number (number of protons).
Isotopes were not known by Mendeleev times, so this discards the last option.
Answer:
Characteristics outlined below
Explanation:
Anthropods, though they generally possess exoskeleton, segmented bodies and joint appendages, are divided into four (4) groups:
- <em>Tracheata</em> (breath through channels in their bodies. E.g. insects)
- Chelicerata (More than four legs, one pir of chelicerae i.e. claw or pincer. E.g. Scorpions and spiders)
- <em>Crustaceans</em> (Have a large rigid exoskeletal, without a circulatory system. E.g. Shrimps, crabs)
- <em>Trilobite</em> (extinct three-headed/lobed marine species)
Get on mathpapa is shows you the answer and how to explain it
Answer:
4 protons, 5 neutrons, 2 electrons
Explanation:
If you look at the numbers beside Be²⁺, the number 9 is the relative atomic mass and the number 4 is the proton (atomic) number. The relative atomic mass is the sum of the number of protons and the number of neutrons.
Number of protons= proton number.
Hence, number of protons= 4
Number of protons + neutrons= 9
4 + number of neutrons= 9
number of neutrons
= 9 -4
= 5
In an atom, the number of protons and electrons are the same since atoms are electrically neutral. But in an ion, the number of electrons is not equal to the number of protons since the atom gains/ loses electrons to form an ion. A positive sign means that electrons are given away.
Thus, Be gives away 2 electrons to form Be²⁺.
Original number of electrons= 4
Number of electrons in Be²⁺
= 4 -2
= 2
In summary, the number of protons and neutrons in an ion is the same as that of the atom. However, the number of electrons is not the same.
