Atomic mass is the mass of an atom, particle, or molecule. The atomic mass is determined by the number of protons and neutrons in the atom. For example, Oxygen has 8 protons (as seen by the atomic number) and 8 neutrons which gives oxygen an atomic mass of 16.
. In single particle problem whole mass is concentrated at a single point so it has a single displacement, single velocity and single acceleration. while, in rigid body mass is distributed
Answer:
A). A few of the positive particles aimed at a gold foil seemed to bounce back off of the thin metallic foil.
Explanation:
Scientists decided to change the model of the atom when they discovered new evidence that showed 'few of the positive particles aimed at a gold foil seemed to bounce back off of the thin metallic foil.' On this ground, <u>Rutherford concluded that atom is mostly made up of empty space and thus, he proposed a nucleus model of atom in which the atom comprises of the tiny and positively charged nucleus is surrounded by electrons with a negative charge</u>. Thus, <u>option A</u> is the correct answer.
Answer:
Option b. Effective nuclear charge increases as we move to the right across a row in the periodic table
Explanation:
The <em>effective nuclear charge </em>is a measure of how strong the protons in the nucleus of an atom attract the outermost electrons of such atom.
The <em>effective nuclear charge</em> is the net positive charge experienced by valence electrons and is calculated (as an approximation) by the equation: Zeff = Z – S, where Z is the atomic number and S is the number of shielding electrons.
The shielding electrons are those electrons in between the interesting electrons and the nucleus of the atom.
Since the shielding electrons are closer to the nucleus, they repel the outermost electrons and so cancel some of the attraction exerted by the positive charge of the nucleus, meaning that the outermost electrons feel less the efect of attraction of the protons. That is why in the equation of Zeff, the shielding electrons (S) subtract the total from the atomic number Z.
The <em>effective nuclear charge</em>, then, is responsible for some properties and trends in the periodic table. Here, you can see how this explains the trend of the atomic radius (size of the atom) accross a row in the periodic table.
- As the<em> effective nuclear charge</em> is larger, in a same row of the periodic table, the shielding effect is lower, the outermost electrons are more strongly attracted by the nucleus, and the size of the atoms decrease. That is why as we move to the right in the periodic table, the size of the atoms decrease.
