Positively charged protons

As the universe expanded it cooled and the positively charged protons and helium nuclei com bined with electrons to give hydrogen and helium atoms Together hydrogen and helium account for 99% of the mass of the universe and 99 9% of its atoms Hydrogen is the most abundant element 88 6% of the atoms in the universe are hydrogen and 11 3% are helium... 

The stmcture of the particles inside the nucleus was the next question to be addressed. One step in this direction was the discovery of the neutron in 1932 by Chadwick, and the deterrnination that the nucleus was made up of positively charged protons and uncharged neutrons. The number of protons in the nucleus is known as the atomic number, Z. The number of neutrons is denoted by A/, and the atomic mass is thus A = Z - - N. Another step toward describing the particles inside the nucleus was the introduction of two forces, namely the strong force that holds the protons and neutrons together in spite of the repulsion between the positive charges of the protons, and the weak force that produces the transmutation by P decay. 

The main chemical elements are listed in Chapter 18. Each comprises a nucleus of positively-charged protons and neutral neutrons orbited by negative electrons. The mass number A is given by... 

An atom is composed of a nucleus, which contains two types of relatively massive particles the positively charged proton and the neutral neutron. The nucleus is surrounded by veiy light, negatively charged electrons equal in number to the number of protons, so that the overall charge on the atom is neutral. The number of protons in an atom, its atomic number,... 

Putting it another way, the adds in successive steps become progressively weaker. This is reasonable it should be more difficult to remove a positively charged proton, H+, from a negatively charged species like H2P04- than from a neutral molecule like H3PO4. 

It is difficult for a positively charged proton to leave a negatively charged anion. The few anions that do act as acids include H2P04 and HS04-. 

When an atom loses electrons, it has more positively charged protons in its nucleus than it has negatively charged electrons mov- ing around its nucleus, giving it an overall positive charge. This %... 

The most successful sensitizers so far tested are complexes of Ru(II) with various derivatives of 2,2 bipyridine, e.g. 2,2 -bipyridine 4,4 -dicarboxylic acid (L). The Ru(II)L3 complex is adsorbed from an aqueous solution of suitable pH value to oxidic semiconductors via electrostatic bonds between —COO- groups of the ligands and the positively charged (protonized) semiconductor surface. 

The negatively charged electrons of the oxygen atom are attracted to the positively charged proton. 

Modem atomic theory teaches that an atom is made up of positively charged protons, an equal number of negatively charged, i much, much tinier electrons, and varying numbers of uncharged j neutrons. Each element has a definite number of protons, and no other element can have that same number. For example, the element hydrogen has one, helium has two, lithium, three, and so on. The number of protons in the nucleus, or center, of each atom, is called the atomic number of the element. 

A negatively charged species will attract a positively charged proton and act as a base. 

Our modern model describes the atom as an electrically neutral sphere with a tiny nucleus in the center containing positively charged protons and neutral neutrons. The negatively charged electrons are moving in complex paths outside the nucleus in energy levels at different distances from the nucleus. These subatomic particles have very little mass expressed in grams so we often use the unit of an atomic mass unit (amu or simply u). An amu is 1/12 the mass of a carbon atom that contains six protons and six neutrons. Table 2.1 summarizes the properties of the three subatomic particles. 

Since the atom is electrically neutral, but is composed of charged particles, the number of positively charged protons and negatively charged electrons are equal. It is the number of protons in an atom that really defines the type of element. For example, all sodium atoms (Na) contain 11 protons and 11 electrons (to keep the atom neutral), but the number of neutrons may vary. Atoms of the... 

A nucleus that has an excess of neutrons will undergo neutron to proton transition, a process that may restore the N P ratio but that requires the loss of an electron to convert the neutron to a positively charged proton, and as a result the atomic number increases by one. The particle emitted is a high speed electron known as a negation (P ) and the atom is said to emit beta radiation, e.g. 

Aufbau principle chem A description of the building up of the elements in which the structure of each in sequence is obtained by simultaneously adding one positive charge (proton) to the nucleus of the atom and one negative charge (electron) to an atomic orbital. auf.bau phn s3-pal)... 

Figure 2.5 Schematic representation of the Au/MPS/PAH-Os/solution interface modeled in Refs. [118-120] using the molecular theory for modified polyelectrolyte electrodes described in Section 2.5. The red arrows indicate the chemical equilibria considered by the theory. The redox polymer, PAH-Os (see Figure 2.4), is divided into the poly(allyl-amine) backbone (depicted as blue and light blue solid lines) and the pyridine-bipyridine osmium complexes. Each osmium complex is in redox equilibrium with the gold substrate and, dependingon its potential, can be in an oxidized Os(lll) (red spheres) or in a reduced Os(ll) (blue sphere) state. The allyl-amine units can be in a positively charged protonated state (plus signs on the polymer...

The positively charged protons are compacted in a tiny, dense center of the atom called the nucleus. The number of protons in the nucleus determines the atomic number for each element. The periodic table lists the number of protons in progression from the first number, hydrogen (jH, with one proton), to the most recently discovered superactinide elements and yet-to-be-discovered elements with the highest atomic numbers. 

Protonation of the alkyne is actually less favourable than protonation of an alkene, because the resulting vinyl cation is sp hybridized, having a bonds to just two substituents, a it bond, and a vacant p orbital. A vinyl cation is thus less stable than a comparable trigonal -hybridized carbocation, since ip-hybridization brings bonding electrons closer to carbon it thus becomes less tolerant of positive charge. Protonation, when it occurs, will be on... 

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